Buster Hymen
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The "Shotgun" and much more...
Rick4095
CARB tuning, part numbers
Diaphragms part number: 1FK-14940-00-00
Shotgun Carb Cleaning Method
http://vmax.lvlhead.com/tips/shotgun.htm
The shotgun method clears the air bleed circuits. The method is not flawed it works very well if you understand how to do it and why it needs to be done in the first place . The reason to do it?...... dirt is getting past the...... air filter...not the fuel filter . Dirt or dust is getting into the air bleeds causing a rich condition. It feels like a spark plug miss-firing until you get up past 8000 rpm and then the bikes runs fine because it now is on the main jet and will take the fuel. If you are not careful and very clean and or do not correct the reason for unfiltered air getting to these carbs the problem will return.--Eric h
Carb Tuning by Roy Richards
If you are really on a budget you can tweak your carbs just a little bit without even removing them and spend less than 50 bucks. I got 4 Hp and a smoother running bike with a better power curve with the following.
First go down to your local bike shop and order a K&N replacement filter for around $40. Stop at radio shack and get a little pack of washers that they sell for around $1. If you don't have a 3/16" drill bit and some masking tape pick that up while you are out.
Remove your fake gas tank cover and both the side scoops. Remove the air filter lid and drop in the K&N filter. Since you are retaining the stock needles DO NOT remove the little Y shaped piece on top of the airbox. By doing so you will end up with about 1 more HP on top but you will have a big hole in the middle of the powerband that you don't want.
Now go to the four little square carb covers that stick out the sides just below the fake scoops. Unless you have a special torx socket you can plan on breaking loose and replacing the one funny looking screw with a pair of vice grips or other creative method. This is an anti tamper screw to keep you from messing with your carbs per Uncle Sam. The other 3 screws should be easy for you. Do the covers one at a time as we do not want to mix up the slides between the carbs.
When you pull one off you will find the following. The cover, a spring, and a slide assembly with a diaphragm attached to it. Be very careful with the diaphragm and notice the little O ring between the outer cover and the carb body. Be sure you put it back on reassembly. Set everything aside and concentrate on the slide assembly. Look down inside the center hole and you will see a plastic screw that holds in the needle assembly. Remove and set aside the plastic screw. Pull out the little spring and the needle assembly. Pull the little plastic piece with the little *** on it off the front of the needle. Find one of the appropriate sized washers in the radio shack washer pack and insert it under the plastic piece you just removed upon reassembly. It goes between what you just removed and the clip on the needle. What you are doing here is raising the needle up in relation to the position of the slide. This will have the effect of richening up the midrange slightly.
There are 3 things to be careful of upon reassembly. First make sure the little plastic *** seats into the little hole in the slide when you drop it back in. Second when you put the plastic screw back into the slide you need to make sure the needle does not set up tight in the slide. It needs to be loose and able to move back and forth a little. You will probably have to take a little bit off of the bottom of the plastic screw in order to keep this from happening. Third notice that the diaphragm only fits in one way. Do all 4 this way.
Now we are going to adjust your idle mixture screws. Take the 3/16" drill bit and wrap the tape around it about 1/4 " from the end of the bit. This is to keep you from drilling too far when we drill out the plugs. Just below the little doohickey (technical **** this is) that sticks out from the covers you just put back on you will see a plug that we need to drill out. Drill it and then use a little screwdriver to pop the rest of it out.
Now you have access to your Idle mixture screws. They are probably set somewhere around 2 turns from bottoming from the factory. Check and record where each one was when you started. As you bring them out the mixture is going to get richer. Try starting them around 3 1/2 turns out. I actually ended up with mine about 4 turns out. This makes the Idle too rich (sounds kinda cool though) but improves off Idle throttle response and drivability. You can set it for a smoother Idle but your drivability and throttle response will not be as good with the stock needles.
When you ride your bike you should notice better throttle response and a harder pull up top. If it had a popping thru the carbs coming off idle that will be gone. You should be able to do this whole job in about an hour and a half with minimum tools and experience. I have since gone to a different setup with a Factory products jet kit but that's another story.
There are two main air bleeds in the carburetors. There are other air bleeds but the ones that give us the most problems are the Pilot Air Jets or PAJ1 and PAJ2. PAJ1 is located on the top of the carburetor. You have to remove the airbox to get to it. If you were sitting on the bike facing forward, it's at the 6 o'clock position, a large oval shaped hole and 4 round holes. Going counter clockwise starting from the oval hole the PAJ1 is the second round hole. It is the one that has the largest brass jet in it. The next hole or the third one in line has a smaller brass jet in it and it is the Main Jet air bleed. The PAJ2 is located behind the slide/diaphragm. You have to pull the cover off the side of the carburetor and pull out the slide/diaphragm to see it. It's the hole with the brass jet screwed in it. It's located at about the 3:00 position next to the oval shaped hole in the top of the housing which is connected to the oval shaped hole in the top of the carb. The PAJ1 and the PAJ2 are connected to the idle circuits of the carburetor. Whenever any dirt or gummed up fuel gets into the air bleed circuits it causes problems. What we can experience is the bike running like it has an intermittent miss or hesitations on acceleration. The blocking of the air jets can also cause other problems if it is severe enough. What to try to correct the problem is...
Pull the air box off. Pull the slide out. Remove the idle mixture screw. Shoot a little carb cleaner in the air bleeds and blow air through the PAJ1, PAJ2, and the hole where the idle mixture screw was. Do this several times. CAUTION: Gas will shoot out of the carbs when blowing in them, so be careful with the eyes and no open flames. Cover all areas that you want to protect against carburetor cleaner chemicals, especially your plastic gauges. When reassembling clean the slides and their bores in the carb body with some WD40. After installing each slide and cover, take your finger and reach in through the top of the carburetor and push the slide back and let it go to see if it moves freely and isn't in a bind and that all four react the same. Install the idle mixture screws and set them at 2.5 turns out initially. Start the bike and then synch and tune the carbs.
Float Level - Roy Richards. All you need is a piece of 25 cent clear plastic hose. Hook it to the drain valve and open it. The fuel outside the bowl in the hose will seek the same level as the fuel inside the bowl. The correct level is measured down from the center of the slide. There is a mark on the side of the carb to indicate this. If it's wrong you get to take the carbs off to fix it. One turn out (air fuel mixture) tells me your float levels are too high.
Correcting a lean condition -Roy Richards
The reason a bike backfires is because it is too lean and not too rich. Your motorcycle has diff carb circuits that control diff parts of the throttle opening and RPM range. When you put the K&N in the bike it will lean out the whole range. This may help you at highway and upper RPM ranges if you really are too rich there. What I found.(and I'm at sea level but it is Hot&Humid which means my air is thin as far as the bike is concerned.) is that I had to fatten up the entire range with my Hindle. Drill out the little adjustment plugs on the pilot screws. Back them out to about 4 turns to start. (The guy with the lean condition on the supertrapp mufflers needs to do this too). This will fix the backfiring and surge or miss down low as it will fatten it up a little down there. Now take the tops off the carbs and pull out the diaphragm and needle assembly. Shim the needles up a little with a pack of little washers you can buy @ radio shack for about $1. Now you will have more mid range roll on power. You don't have to pull the carbs to do either of these things and your bike should run way better....
What is the negative effect of raising the needle too high? Runs too rich.--Sam Blumenstein #795.
Mixture is too rich, less power, lower mileage, weak response. The closer you get to right mixture, throttle response is quicker, sound of exhaust is sharper.--Don "Old Man" Smith #2
Ok I finally got my 42.5 pilots and installed them. Still wayyyyy too lean. My plugs are white as ghosts. My pilot screws are currently 3.5 turns out with the 42.5's Ok here is what not to do. While I was waiting for my 42.5's I taped up my morley air filter and went wayyy
rich. took off the tape and way lean again. Then I took a #76 drill bit and bored out my pilots (old virago trick)...that made my plugs black and sooty LOL. If I put 150's(mikuni) in the paj2's my midrange goes way too rich...off the chart rich...I currently have the 177.5's in my paj2, not sure what they are doing yet. I have sprayed wd40 on the intake boots and the bike doesnt seem to die out, so I don't think I have an intake leak, also if I did I probably would not go way rich in my midrange. So here is the current set upMains
J170 Pilots:42.5 PAJ2:177.5(mikuni) PAJ1:stock Stage7 Needles, morley air intake Float Level: 16mm (same results at 17mm)Kerker 4-2-1 w/2.5" baffle. Any ideas. Oh a side note bike only dyno's out at 90hp and compression is good.
Try putting the MKNI 170's back in the paj2, see what that does, then, try taping up smaller sections of the airbox, see what that does. Honestly, if you have 42.5's in there and it's still lean, (even with the large paj2 and full box mod ) your pilot circuit is likely still not completely open. I had a set of carbs that were so bad i had to take craft wire (very small guitar string type stuff ) and push it through the circuits with intermittant sprays of cleaner to get them completely open. Look at the exploded view of the carbs to see where the pilot and bypass circuits run. i went in thru both the pilot screw and bypass holes at the front of the carbs and in thru the exit holes in the throats of the carbs. Down thru the paj1 and worked on the jet blocks too. If you can turn any of the screws in and make little to no diff. to the engine idling under 1000rpm, the pilots are not completely open and you are running on fuel sneaking around the needle jet from the main. Especially if you have the needles at or higher than 3rd clip. --steve
Low speed Carb tuning - Justin Lassy
The fuel mixture screws are indeed located behind the brass plugs. The brass plugs must be removed to access the screws. Be *very* careful about drilling out the plugs-use a drill stop. If you hit the screws with the drill bit, even for a moment, you risk running the screw down hard against its seat, destroying the screw and possibly the carb seat. Bad. The fuel mixture screws deal w/ mixture at idle and a little bit above idle. They will determine off idle throttle response and extremely low idle cruising. Turn screws in to lean the mixture out, turn them out to richen the mixture. Here are some rough guidelines to determine if you are running rich or lean at various RPM's. Examining the plugs is really the best way to get accurate results, but these guidelines will help you shoot for a direction (leaner or richer).
Idle and off idle: Lean condition: Poor off idle throttle response, idle that flutters a little after a throttle blip then slowly returns to the idle that you've set, popping back through the carbs when the throttle is blipped.
Rich condition: Off idle response may be good unless plugs are fouled from a way too rich mixture. After a throttle blip the motor will dive down below set idle and will either die if way too rich or may return to set idle if it can recover.
Setting the pilot screws - Jim Younghusband
For me, the easiest way to set the idle mixture screws, is to run the motor until warm and idle stable. Run each screw in, one at a time, until the engine stumbles, back the screw out until just rich of peak idle (idle drops again). Then run them back in to peak idle. Repeat for each carb. If your screws are out more than 3 turns, I feel the jet needs to be swapped to the next larger. Your final position should be around 2.5 turns out.
Pilot screw adjustment vs. Carb sync -Terry Campbell
The pilot screw adjustment and the carb sync are really different adjustments all together. If you had never done a carb sync it was probably good advice to do it once before fooling with the mixture/pilot screws... or anything else. The carb sync is intended to equalize the opening of the carburetor throttle plates, (this is beneficial throughout their range of operation).
The reason you see different recommended mixture/pilot screw setting in the manual for the different models is because these bikes all have different size pilot air jets, (primary ... the one on the top of the carb ... the secondary pilot air jet is the same on all models and it hides behind the slide rubber inside the carb). Air from "both" of the pilot air jets mix with gasoline from the "pilot fuel jet" to produce the mixture that you control with the mixture/pilot screw, (except when you open the throttle a little .. because there is a bypass hole .. but that is another story).
The reason you'll find the screws set differently in each carb is because at the factory, (hopefully), they set these precisely using a CO meter connected to each cylinder via the little 1/4 pipe plugs you see in the factory exhaust pipes. These differences make up for the uniqueness of each carburetor and cylinder it is attached to, (rather unavoidable .. as minute as it might be). Cranking these screws out beyond where they might have been set originally will increase the CO readings for the respective cylinder, (make it richer at idle). Even though there might be other ways to achieve your objective ... this works pretty good for adding additional fuel at off idle ... and at light, (no load ), up to about 1/8 throttle throughout your mid-range, (which hopefully you will find beneficial).
There is a limit to this benefit and if you do more to your intake etc you may find you need to do something more substantial for you light throttle fuel requirements and do something different, (like make one of the pilot air jets smaller or the pilot fuel jet larger etc). As most of these bikes have the pilot screws set on the "lean" side for emission purposes you will hopefully benefit to some extent by backing them out a little. The models with the bigger primary pilot air jets etc are going to require a little more twist to achieve a comparable mixture result, (unless you are doing the ear routine or have your own $125 JCWhitney CO meter).
Air / Fuel Mixture: The power at wide open throttle above 7000 rpm is around 12.8, not 13.8
The pilot circuit is fed into the manifolds below the throttle plate.. For many this is one of the hardest circuits to dial in for off idle or throttle response because the pilot circuit overlaps into the enrichment circuit as soon as the throttle plate is opened... the enrichment and following circuits all overlap to the next circuit and all are sensitive to velocity, not rate of air flow.I myself use the mercury stick because they give me a wide range of revving (blipping) the throttle to the point where velocity creates the vacuum needed to compress my slide springs. This gives me the best WOT right off idle... if I am tuning a bike and it's off on one of the pilots, rich/lean condition will be seen when the cylinder spikes on the mercury. Then I can make the adjustment. But still, we need to watch the tack because although we get it all equal doesn't mean its right... they can all be too rich/lean... at quick blip, the needle should rise up then drop to the set rpm, not float or hang or fall below the set rpm. And like I said in past posts, don't be surprised if one pilot is .5 turns and another is 3 turns, this is normal... only way they will all be the same is if the valves are tuned.-Paul
Carb Rebuild
Clean all four carbs?, did you disassemble the 4 carbs from the side rails or just broke them down to tow pairs? Did you remove All the jets?? When you re-assembled them did you make sure the side plates were tight? you first mistake was not syncing the carbs first!!, every time you that carbs off and or apart the sync gets thrown off, and depending how much pressure was used to get them back in the boots can a will throw them off even more, your best bet now is remove the carbs, flip them over and see how the throttle plates are relative to the bores, I'll bet you'll find them all out of adjustment, some or not all, of them will be open too much, adjust all of them back down to almost fully closed, then re-install, warm up engine and sync the carbs FIRST THING!!
stock is 152.5 mikuni jets.. you're running dyno jets. 175 is very rich for a 4-2 system... the dyno jets instructions will get you in the ball park. those instructions are as old as the bike, the new pipes aren't even listed and there's been a significant change to the needle spacer that dynojet don't know about... what I would do with stg 7 marks pipe is start out on the 2 clip (depending on the bike year), in many cases 2 is too lean and 3 too rich.. So I came up with the needle shim kits (and sold a lot of them)... these shims will give you a true 1/2 clip... use the stock mains... if too lean go to the 155 mains... set the floats 17mm if you want maximum power you need to adjust each circuit for a smooth transition through out the range.. this is where you will get power... the engine should accept full throttle from any rpm. at wide open throttle it should tach out in a heart beat. don't tune for big dyno numbers... tune for a good agressive curve with no dips.
It depends on which 165 main jets you have. I would bet they are 165 dynojet jets which are very similar in actual size to the Mikuni 152.5 main jets (they are rated differently). You can id them by looking into the end of the jet and see if the hole is "flush" to the jet or if there is a bit of "countersink" to them. Either way, the 152.5 works well 99% of the time with most configurations (stock or header) unless you have slip-ons which then smaller jets tend to work better.
Muscle Jet Kit:
New "Panel Filter" (K&N or Air Hog) - installed into your airbox lid
Air Correctors
Lighter Springs
Drill bit (for the slides)
Large Selection of jets (6 sizes)
The stock needles work just fine even with this setup and produce stage seven power with V-boost still fully intact. Mileage is in the 40's. HP is in the 120's. Torque is in the low 80's high 70's. Easy to install and tune in (if you can take carbs off and have the ability to sync them).
Factory Pro, CV Carb Tuning
Follow steps in order....First, dial in:
1. Top end (full throttle / 7.5k to redline -
Best Main Jet must be selected before starting step 2 (needle height)!
Select Best Main Jet
To get the best, most even top end power (full throttle/after 7500 rpm), select the main jet that produces the highest top speed / pulls hardest at high rpm.
If the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. Install a smaller main jet and retest until you find the main jet that pulls the hardest at high rpm when fully warmed up. This must be done first - before moving on to the other tuning ranges.
If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small.
In order to properly tune the midrange and low rpm carburetion, THE MAIN JET MUST FIRST BE PROPERLY SELECTED after 10 to 15 minutes of hard use!
Do not pay too much attention to the low-end richness when you are changing main jets - you still need to be using the main jets that produce the best power at high rpm. You will deal with the low-end / cruise later - after step 2.
2. Midrange (full throttle /5k-7k)
Step 1 (Best Main Jet) must be selected before starting step 2!
Select best needle clip position
To get the best power at full throttle / 5k-7k rpm, adjust the needle height, after you have already selected the best main jet.
If the engine pulls better or is smoother at full throttle/5k-7k in a full throttle roll-on starting at <3k when cool but soft and/or rough when at full operating temperature, it is too rich in the midrange and the needle should be lowered.
If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k.
If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set.
Do not pay too much attention to the low-end richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle / 5k-7k power in conjunction with the main jets (Step 1) that produce the best power at high rpm. You will deal with the low-end / cruise next.
3. Low end (full throttle / 2k-3k)
Step 1 (Best Main Jet) and Step 2 (needle height) must be selected before starting step 3!
Float height (AKA fuel level & how to..)
To get best low-end power, set float height (fuel level) so that the engine will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum.
Float heights, unless otherwise specified in the installation guide, are measured from the "gasket surface" of the carb body to the highest part of the top of the float - with the float tang touching but not compressing the float valve spring.
If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm, that gets worse as the engine heats up, lower the fuel level by resetting the float height 1mm greater (if the original was 13mm - go to 14mm). This will lower the fuel level, making full throttle / 2k-3k rpm leaner.
If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.
Example: change float height from 15mm to 14mm to richen up that area.
REMEMBER, since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting.
Warning: If the engine is left with the fuel level too high,, the engine may foul plugs on the street and will be "soft" and boggy at part throttle operation. Adjust Floats to raise/ lower the Fuel Level.
Base settings are usually given if a particular application has a history of fuel level criticalness. The Fuel level height in the float bowl affects full throttle/low rpm and, also, richness or leanness at cruise/low rpm.
Reference: a bike that runs cleanly at small throttle openings when cold, but starts to show signs of richness as it heats up to full operating temperature, will usually be leaned out enough to be correct if the fuel level is LOWERED 1mm. Check out and RESET all: Suzuki (all), Yamaha (all) and Kawasaki (if low speed problems occur). Needless to say, FUEL LEVEL IS EXTREMELY IMPORTANT!!!
If there are low-end richness problems, even after lowering the fuel level much more than 1.5mm from our initial settings, check for needle wear and needle jet (part of the emulsion tube). See Worn Needle and Worn Needle Jet diagram. It is VERY common for the brass needle jets (in the top of the "emulsion tube") in 36mm, 38mm and 40mm Mikuni CV carbs to wear out in as little as 5,000 miles. Check them for "oblong" wear - the needle jet orifice starts out round! Factory Pro produces stock replacement needle jets / emulsion tubes for 36mm and 38mm Mikuni carbs.
4. Idle and low rpm cruise
Fuel Screw setting (AKA mixture screws)
There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil. Cap removal details. Newer Honda carbs have no caps, but use a special "D" shaped driver, usually supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation. (pj tuning information)
Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
NOTE: A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
NOTE: A lean problem gets better as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!
Carb Kit Design is a combination of science, art, intuition and and at times, a fair dose of wizardry. There is no dyno that "tells" one how to assemble or modify the carb to deliver proper power and response.
Perfect Carb Kit TUNING requires patience and perseverance and "reasonable" feel to feel the changes - of which - most motorcycle riders have a good ability to do.
When a dyno "operator" says he/she has to ride the bike after dyno tuning to do the final tune for cruise smoothness - that's what they are doing. Avoid any dyno operator who says that they don't have to do that!!!
The only dyno that I know of that will duplicate and visually display the engine smoothness is the EC997 dyno (yes, I know, we make it) - that's one reason why, if you can, you'd like to use one for tuning - a smoother engine IS getting the best mixture. Other dynos claim to "tune to an "A/F Ratio" - probably the biggest marketing scheme in the dyno industry at this time - and they never can equal the quality of tune as designed -These tuning kits have been thoroughly tested to ensure easy, trouble-free, optimized performance.
Please note: If you have installed the kit and gone through the optional screw settings, clip positions and main jets, and still have a persistent flat spot/problem, we ask you to call us. Unique engine / exhaust / filter / altitude / temperature combinations may require individualized setups. We are here to help. The information gained to your solution will be installed in our computerized reference database. PLEASE CALL!
We (Factory Pro) ask that upon completion of installation and tuning, that you call us with specifications of your installation, (pipe brand, filters, advancer, altitude, humidity, temperature and final carb settings) to be entered in our TUNING DATABASE. The database allows us to include the "most used" jet sizes and setup specifications in every kit. Use (415) 491-5920, (800) 869-0497 or fax (415) 492-8803.
Jets / Jetting
Pilot jet 37.3
Pilot air jet1 is 90
Pilot air jet2 is 170
Main jets have little or nothing to do with fuel mileage unless you are riding above 7500 rpm all of the time.
Fuel mileage is mainly a result of..... in order of importance
# 1 Float bowl fuel level...17mm...never over or higher than 16.5 mm
#2 Mixture screw settings... As lean as possible. Set up your carbs...then take a ride and adjusting each carb one at a time. With the engine at operating temperature Start with one carb and turn in the mixture screw a very very small amount at a time ....turn it in a hair..then ride it . Turn it in some more then ride on ....keep doing this until the carb starts to spit back when you accelerate or take off from a stop...then back out the screw a bit at a time till it stops spitting ....When done go to the next carb ....it takes a while to do this . I just carried a small screw driver in my pocket for a few rides and kept working with the screws. This is how we get over 40 mpg. When it is right the bike will be cold natured to start even in the middle of Summer and will idle smooth when warm. I always just smile when someone tells me how well their bike is in tune because it does not need the choke to start.
#3 Needle setting or depth and the condition of the needle and its receiving jet. Stock is stock....If your needles are adjustable then if ....White in color retainer ...1.5 to 2nd notch...beige in color 2.5 to 3. is a good setting starting point with an open exhaust .
#4 Fresh spark plugs....use the stock plugs and change them at least every other oil change....I do mine every oil change ...They are cheap and the bike runs crisp
# 5 a good and perfect valve adjustment helps a lot too if they are out....it also makes tuning easier if all the cylinders are making equal pressure as a result of valve adjustment
As you can see....Main jets are not in the picture. If your main are Mikuni jets ....160 is way too big for your set up ....but if they are DynoJets they are just about right on.
With this set up you too can get over 40 mpg cruising at 80 mph + My bike with stg 7 got an average of between 130 to 140 miles to the red light all the time. Even hammering on it all the time in the mountains got well over a 100 miles to the light It is a matter of keeping it in tune.
Highway steady cruise should be above 40mpg.. mid-range is where we do most of our riding and the needle position in the needle jet is important considering that both mid range and top end mix is delivered through the needle jet where the jet needle meters the flow into the venturi for the final mix.. if your using aftermarket needles adjust the clip to get a little more needle into the needle jet--paul
The mercury sticks are vacuum sensitive and basically designed to synchronize the 4 carb butterflies. With butterflies varying in seated position you will see a different vacuum signal from each engine cylinder. By equalizing the throttle blade openings (synchronizing carbs) you will see the vacuum signal equalize so that all carbs are as equal as possible through the throttle range. This means each cylinder sees, as close as practicable, the same amount of throttle at all openings. Which in turn sees each cylinder having the needle the same position in jet etc. throughout the throttle opening range. Basically this means each cylinder has the same fuel curve as the others. That's the aim of synchronizing the carbs. It's a mechanical adjustment so equality of carb operation to each cylinder occurs.
The idle screws are basically pilot or idle circuit fuel curve adjusters. The idle circuit caters for idle through to about 1/2 throttle or so when the fuel curve is influenced more by the needle and main jet. I'm not an expert on these carbs so others can be more specific but from my experience the idle screws will only have an effect on vacuum as you close them down too much or open them up too much causing excessively lean or rich mixtures respectively. You don't really need a vacuum gauge to measure this; it is very obvious in that the bike starts running rougher when you go too far with any of the individual pilot screws. As many like Paul and Don have said before, you need to turn each screw in fully till the engine stumbles and roughens up then back out till it stumbles with too rich a mixture and go back in till you have the smoothest possible running. Do this with each cylinder screw in turn and don't panic if some of the screws have a lesser effect as you go in or out. Just try to end up with the smoothest idle and blipping the throttle should leave the bike with the tach needle dropping back down to a clean idle rather than dropping below idle speed and rolling back up (too rich) or hanging up after blipping the throttle and slowly returning to a good idle (too lean). The only other way to do this is to have an accurate A/F ratio gauge setup in each exhaust header. We do this on the engine dyno on extreme performance and race engines every day.
As I said I'm not a Vmax carb specialist but doing this sort of tuning with the carbs often enough you will get used to where the bike runs best. Unfortunately there are many more variables effecting this like how well the valves are set (effects cylinder vacuum), even compressions on cylinders, condition of carbs in general like clean idle circuits, correct float levels, coasting enrichment assembly operation, condition of carb diagrams, condition of needles and main jets (they wear into each other over time) and more.
We need a decent fuel injection system frankly. Set it and forget it, although for the big engines I do like the 39mm flatslides. They are more temperamental than the stock carbs and need constant adjusting (I like doing this anyway) but because they are fully mechanical they respond exactly to changes unless they have too much internal wear.--Sam Blumenstein #795
I'm having idle problems with my #3 carb. I get a random idle if I completely open the mixture screw. Everywhere else, no idle. Every other circuit is fine though. I can accelerate fine everywhere else...it's just steady cruise or small throttle below 4000 rpms. Before, I had the screw set to about 4.5 to 5 turns before the cylinder idle. I've replaced the sparkplug, checked ignition and it's firing perfectly, compression is about 180 psi. I did the shotgun and that didn't help at all. Float level is spot on. I'm going to check the enrichening plunger, maybe it's stuck open. Other than that, going to break open float bowl and remove jet block. Could be plugged pilot fuel jet. Maybe a piece of gasket is blocking one of those holes.
Answer to problem turned out to be: Blocked purge jet.--Eric h
I'll check that again. I did as you suggested before, use straw and blow in all 3 holes and listen for air. Could be blocked now I guess. You said once before that carb cleaner doesn't work for those right? To use small wire? What gauge of wire did you use? It's still amazing to me that those small purge jets cause so much trouble.
Do not know ..gage....small wire is found here at Craft store....The hole behind the diaphragm on left side is the one that gives the most trouble....if blocked completely there will be a small amount of fuel when you pull the cover off. Remember you are dealing with a carburetor for a high performance 300 cc motor. -Eric h
I'm writing an article for the next Vboost but thought I would share some findings here first:
Morley Pros:
- Velocity stacks richen you up everywhere, mask some low-end carburetion problems
- Cheaper product ($200)
- works well with stock main jets if using DJ needles
- also works well with stock needles
- works best with stock vboost
- Vmax seems to like the airbox and velocity stacks
- change of humidity/temp isn't noticeable, no jetting changes necessary for cooler temps
Morley Cons:
- Velocity stacks richen you up everywhere
- more work to tune low end carburetion (I think bigger PAJ1 would help, didn't have the jet selection to try)
- bigger mains (Mikuni 162.5's in my case) are needed with stock non-adjustable needles
- open vboost makes low end richness problem worse
Stage 7 Pros:
- Works with stock or open vboost
- easier to tune low-end
- works well with stock main jets
- intake noise gives me a chubby
- works best with open vboost
Stage 7 Cons:
- Expensive ($300 - $450 depending on vendor)
- more filters to clean/oil
- supplied puke bottle is cheesy looking
- you can smell the blow-by crank gases
- more temperamental to changes in weather --Mark Milne #1098
this thing is killing one carb back ride side as you sit on the bike is spitting up and wont sync i had the carbs apart and cleaned everything i just dont get it and i'm thinking then fuel is ok but way out of sync I think i'm done with this no fuel injection crap i have done this before with no problems stage 7 with 165 jets in and needles set on 3rd clip it almost souns like a miss but the spark plugs are new today'
what yr. ? are you sure you have all the intake connections seated and tight ? how about the slide diaphram, you didn't happen to loose one of the little springs that are on the synch linkages ? if you have the vboost hardware in and can close it , it will be easier to work out.
i have seen something similar to this before after extensive carb work and the synch was very far off. sometimes you need to use the idle speed set screw to keep it running until you can get the synch closer. just to cover the basics, the left front carb is the control, it is non-adjustable. the left rear is synched to match the left front. then without regard for the left
side levels, the right front and rear are matched to one another using the rear synch screw on that side. then the right side is matched to the left with the front synch screw on that side. but
you've done that before and now and still have problems. spitting back up through the carbs is a lean issue that could be that that cylinder is way out of synch, a vacuum leak or a blocked main air jet (top of carb), problem at diaphram or paj2 or a clog in the pfj or the bypass circuits between it and the pilot screws and / or the outlets into the venturi's. sorry this doesn't seem to track it down much but it gives you places to look.-Steve
Needle Adjustment
Do 2.75 clips from the blunt end of the needle. Do the needle test as Don suggested. Here it is:
1) 4th gear, 4K RPMS: WOT until 6K RPMS; let off throttle and if it speeds up, running rich and lower the needle.
2) 4th gear, 4K RPMS: WOT thru 6K RPMS; at 6K, give it some choke; If it speeds up, running lean and raise the needle. If neither condition happens, needle position is fine.
While in 4th gear rev to 4k. Open her up to 6k. Turn choke on and do the same thing. Did power get better or worse? If it got better...too lean raise needle. Worse too rich lower needle.
Carb Tuning
well, Dale is no different than any other vendor that sells products. Only thing that bothers me is his lame jet kit. 4 washer, 4 big main jets and a filter for how much? This kit will richen the hell out of the mix. Rich is smooth and most buy into it with a pipe thinking their
bikes run great. I removed more DW power kits then I can remember and the owners were freaked about how much power then gained. The dyno jet stage one isn't bad as far as needles, spring, and slide drilling. One can cure a rich condition by leaving the main jet stock and adjust the needle to meter the mix to the lean side. There is no majic top end running on mains only, the main jet pilots the fuel to the needle jet but the jet needle controls how much mix enters the venturi for final air mixture. So what are we doing when we lower the main jet but increase the needle height? The main jet will control the flow at top end but mid-range will be rich. So best to leave the main stock, get a set of adjustable needles and pilot the flow from there. Another thing we can do is.....If you have a post 93 max with fat needle spacer and its rich, find a set of pre 93 needle spacers and lean it out. Vise versa with the lean
condition on a older max. Its all about tuning. Stage 7 is the best way to get a fine tune but there is nothing wrong with the stock airbox tuning either. The bike is set from the factory for a wide range of temps and altitute conditions. It will run and for most it will run good but, what bad if we dont know good. We recommended so tuning for someone at 5000 feet. PAJ#1 went from #90 to #100, needle was adjusted with a smaller spacer and the PAJ#2 was increased. This person claims his bike runs like a bat out of hell. I believe him, jetting should be adjusted along with the shift lever and brake pedal-paul
Before changing anything I would take your carbs off and see what you have. Check the size of the main jets (152.5), the pilot air jet #1 at the top of each carb (90) and pilot air jet #2 behind the slides (170). It's very likely that the previous owner just dropped in bigger jets all around thinking that more fuel equals more power. Check your float levels too. Make sure all four read the same....either 16 or 17 mm. Here are a couple of links to get you started in the inards of Vmax carbs:
http://vmax.lvlhead.com/tips/carb/walsh/walshcarbs.htm
http://vmax.lvlhead.com/tips/shotgun.htm
http://imageevent.com/wforest/carbswhatamess;jsessionid=qx8h4ccve2.zebra_s
Mark Milne #1080
Determining Rich / Lean Conditions
your too rich. Even the 150's are rich for your altitude...152.5's make it worse especially past 7500 rpms. The general rule is to decrease main jet size by 1% for every 1000 feet of elevation. 152.5's are great jets for sea level but not for you. So, I'd put 145 mains in. Then, I'd make sure your floats are all set to 17 mm. Some guys in your area have messed with the pilot air and fuel jets but I don't think it's necessary unless you can't get a good idle mixture by using the mixture screws. On your '85, how was the airbox modified? Try removing your "Y" and see how that does too. After your main and floats are correct, do the following test for your needles.
1) 4th gear, 4K RPMS: wide open throttle until 6K RPMS; let off throttle and if it speeds up, running rich and lower the needle.
2) 4th gear, 4K RPMS: WOT thru 6K RPMS; at 6K, give it some choke; If it speeds up, running lean and raise the needle.
If neither condition happens, needle position is fine. If you need to lean the needle your outta luck since stock needles aren't adjustable. I'd look at getting stock Canadian Vmax needles or DJ stage 1 needles. These are adjustable. You could use Factory Pro but they're titanium and will wear out your needle jets over time. Valve adjustment will help out too. I noticed the biggest difference when i adjusted my valves. Make sure all the intakes are the same....same with the exhaust valves. --Mark Milne #1080
STAGE 7
Use the pauls pea shooter method next time you start the bike. turn your pilot screws out 2 full turns. choke on start the bike, squirt sea foam in the choke vent at the top of carb, this will be the hole above the choke valve. do this while its running, no reving but keep it around 1500rpm.. now, once bike is warmed up, choke is off, squirt sea foam in the Pilot air jet #1.. this is the removeable jet at the top.. slight revs will allow the engines vacuum to draw the sea foam down the air circuit to clear it up.. if you should get sea foam into the carb throat dont worry about it, you will have some smoke out the exhaust is all but it wont hurt anything.. once done set the screws back in 2 whole turn where you had them. you dont want to use compressed air. compressed air will force and dirt into the circuit and clog things worse and once the enrichment is plugged, forget the address... 175 is too big, use the mikuni 150 or 152.5. The main jet gives good power to the low to mid range? you are misinformed. Your pilot screws and needles are adjustable to calibrate the best mix in these ranges.. these 2 ciruits are the most crucial and its not as simple as dropping in different mains to get dial them in. I suspect the bike has yet to see its full potential. Follow instructions above, if that helps close the boost and synchronize the carbs.. once that is done open the boost back up.
Once you got it going let me know. I will dial you in the rest of the way. Things to document, what needle clip, what PAJ#2 under the slide? -Paul
Check the air filter, see that you have Mikuni 170 jets at paj2,synch the carbs and adjust the pilot screws as close to 2.5 turns out or under as you can get them without spitting back thru the carbs or sluggish off idle. -Yarddog
Took my bike (2000) out for the third ride of the season and is was running great as it was on the last two rides. All of a sudden, it started to miss or sputter between 4 and 6000 rpm. As soon as v-boost kicked it, it took off like a rocket. Took it out today for a little ride, and it was doing same thing.
your mission today is to remove the airbox cover to get a visual on the carb slides.. sounds like one or 2 are hanging up.. -Paul
Carburetors Removal
you must take off the carbs. It's easiest when you break them into pairs. Once the carbs are off the bike, remove small e-clip holding choke linkage rod onto carb #4. Then, remove e-clip plus washer from sync rod. Then remove front and rear bracket (4 screws each). Finally, disconnect "T" fuel hose that links left and ride sides. reak open the culprit carb bowl and the other one that's a part of that pair. Flip the pair upside down and set on level surface. Then use the picture I included and make sure the 13 mm carb distance matches the 16 mm. Using a digital caliper makes it pretty easy. hen you put the carb back on, you'll have to sync your carbs. et us know how you come out. -Mark, #1098
i put a new ufo 4 into2 exhaust on my 85 stage 7 max, i had a 4-2-1 kerker on it but with only a 1-1/2" baffle.. it ran strong and fast but the pipe is worse for wear and needed to be replaced, redone,(ill put it on my 98 when im finished)..anyways, i was hopin to get some suggestions as to my carb stup to gain some of the power back ..i have 175 mains in now and i believe the needles are set at 3rd clip down from blunt end.. i seem to have decent power up UNTIL 4000 rpm then i lose all power, it will accelerate but with no pull or excitement, nowhere close to my kerker, i know the kerker is better for power BUT there should not be this much of a difference.. im in ontario canada so elevation is about 300 ft or so..at around 7or 8000 rpm it picks up power again but not a LOT, is my major problem in my needle height?
I have a 98 full stg7,4-2 Marks, and my mid rang is on par with a stock Max, but I spend little time there. At 5 grand it starts pulling hard, and at 7 grand to 10 grand I'm glad to have a stepped seat as the tach lunges forward on a second hit, and my fingers stretch. After much experimenting I ended up with using DJ-175 mains (no, its not rich), and dJ needles on top (leanest) clip. Also, if mileage went to crap, another indicator of rich. When I went from Supertrapps to a full header it richened the mix, and my clip was on the same place as yours, and raising it to the top corrected it. And the needle position DOES affect mid range and top end. --Randy3539
Some run stage 7, open boost...170's or DJ190's. Some run stock vboost with 170's and 190's. Some run tboost with 170's or 190's. Try it with the 170's. If running rich at off-idle or at 4-5000 rpms at small throttle angles then increase the PAJ2.--Mark#1098
I purchased the Morgan Carbtune and received it about two weeks ago. Just finished using it to sync my new EFI throttlebodies on Sunday. What a great and easy to use tool. I sync the #2 to #4 and then #1 to #3 and then 2/4 to 1/3 and really worked well.--RickRash#1283
The tubes are connected to the spigots, engine running and idle set, what does the gauge reading mean?
1. Use a light blipping of the throttle to see where the four SS rods settle.
2. If you have not synchronized for awhile they will probably be slightly uneven. The bigger the variation the more out of sync the carbs are with each other.
3. To sync the carbs, start with the back left carb (#1), (NOTE: the front left carb (#2) is the Master Carb on the Vmax, and all others have to be adjusted to match it) making adjustments to its set screw to the point where the rods are the most even. At that point you will move to the right side, do the same for carb #3 (back right) and carb #4 (front right) and then move over to the left side carbs, doing one again. Slightly blip the throttle after each adjustment to see the affect. The left side and right side carbs are linked together, so it may take a number of time, moving back and forth to each side.
4. The carbs are very sensitive to adjustment. Adjust one carb at a time and then check the reading. Give the gauge a few seconds to settle after each adjustment. It is generally necessary to gently blip the throttle to seat the carb that has jut been adjusted.
Rick4095
CARB tuning, part numbers
Diaphragms part number: 1FK-14940-00-00
Shotgun Carb Cleaning Method
http://vmax.lvlhead.com/tips/shotgun.htm
The shotgun method clears the air bleed circuits. The method is not flawed it works very well if you understand how to do it and why it needs to be done in the first place . The reason to do it?...... dirt is getting past the...... air filter...not the fuel filter . Dirt or dust is getting into the air bleeds causing a rich condition. It feels like a spark plug miss-firing until you get up past 8000 rpm and then the bikes runs fine because it now is on the main jet and will take the fuel. If you are not careful and very clean and or do not correct the reason for unfiltered air getting to these carbs the problem will return.--Eric h
Carb Tuning by Roy Richards
If you are really on a budget you can tweak your carbs just a little bit without even removing them and spend less than 50 bucks. I got 4 Hp and a smoother running bike with a better power curve with the following.
First go down to your local bike shop and order a K&N replacement filter for around $40. Stop at radio shack and get a little pack of washers that they sell for around $1. If you don't have a 3/16" drill bit and some masking tape pick that up while you are out.
Remove your fake gas tank cover and both the side scoops. Remove the air filter lid and drop in the K&N filter. Since you are retaining the stock needles DO NOT remove the little Y shaped piece on top of the airbox. By doing so you will end up with about 1 more HP on top but you will have a big hole in the middle of the powerband that you don't want.
Now go to the four little square carb covers that stick out the sides just below the fake scoops. Unless you have a special torx socket you can plan on breaking loose and replacing the one funny looking screw with a pair of vice grips or other creative method. This is an anti tamper screw to keep you from messing with your carbs per Uncle Sam. The other 3 screws should be easy for you. Do the covers one at a time as we do not want to mix up the slides between the carbs.
When you pull one off you will find the following. The cover, a spring, and a slide assembly with a diaphragm attached to it. Be very careful with the diaphragm and notice the little O ring between the outer cover and the carb body. Be sure you put it back on reassembly. Set everything aside and concentrate on the slide assembly. Look down inside the center hole and you will see a plastic screw that holds in the needle assembly. Remove and set aside the plastic screw. Pull out the little spring and the needle assembly. Pull the little plastic piece with the little *** on it off the front of the needle. Find one of the appropriate sized washers in the radio shack washer pack and insert it under the plastic piece you just removed upon reassembly. It goes between what you just removed and the clip on the needle. What you are doing here is raising the needle up in relation to the position of the slide. This will have the effect of richening up the midrange slightly.
There are 3 things to be careful of upon reassembly. First make sure the little plastic *** seats into the little hole in the slide when you drop it back in. Second when you put the plastic screw back into the slide you need to make sure the needle does not set up tight in the slide. It needs to be loose and able to move back and forth a little. You will probably have to take a little bit off of the bottom of the plastic screw in order to keep this from happening. Third notice that the diaphragm only fits in one way. Do all 4 this way.
Now we are going to adjust your idle mixture screws. Take the 3/16" drill bit and wrap the tape around it about 1/4 " from the end of the bit. This is to keep you from drilling too far when we drill out the plugs. Just below the little doohickey (technical **** this is) that sticks out from the covers you just put back on you will see a plug that we need to drill out. Drill it and then use a little screwdriver to pop the rest of it out.
Now you have access to your Idle mixture screws. They are probably set somewhere around 2 turns from bottoming from the factory. Check and record where each one was when you started. As you bring them out the mixture is going to get richer. Try starting them around 3 1/2 turns out. I actually ended up with mine about 4 turns out. This makes the Idle too rich (sounds kinda cool though) but improves off Idle throttle response and drivability. You can set it for a smoother Idle but your drivability and throttle response will not be as good with the stock needles.
When you ride your bike you should notice better throttle response and a harder pull up top. If it had a popping thru the carbs coming off idle that will be gone. You should be able to do this whole job in about an hour and a half with minimum tools and experience. I have since gone to a different setup with a Factory products jet kit but that's another story.
There are two main air bleeds in the carburetors. There are other air bleeds but the ones that give us the most problems are the Pilot Air Jets or PAJ1 and PAJ2. PAJ1 is located on the top of the carburetor. You have to remove the airbox to get to it. If you were sitting on the bike facing forward, it's at the 6 o'clock position, a large oval shaped hole and 4 round holes. Going counter clockwise starting from the oval hole the PAJ1 is the second round hole. It is the one that has the largest brass jet in it. The next hole or the third one in line has a smaller brass jet in it and it is the Main Jet air bleed. The PAJ2 is located behind the slide/diaphragm. You have to pull the cover off the side of the carburetor and pull out the slide/diaphragm to see it. It's the hole with the brass jet screwed in it. It's located at about the 3:00 position next to the oval shaped hole in the top of the housing which is connected to the oval shaped hole in the top of the carb. The PAJ1 and the PAJ2 are connected to the idle circuits of the carburetor. Whenever any dirt or gummed up fuel gets into the air bleed circuits it causes problems. What we can experience is the bike running like it has an intermittent miss or hesitations on acceleration. The blocking of the air jets can also cause other problems if it is severe enough. What to try to correct the problem is...
Pull the air box off. Pull the slide out. Remove the idle mixture screw. Shoot a little carb cleaner in the air bleeds and blow air through the PAJ1, PAJ2, and the hole where the idle mixture screw was. Do this several times. CAUTION: Gas will shoot out of the carbs when blowing in them, so be careful with the eyes and no open flames. Cover all areas that you want to protect against carburetor cleaner chemicals, especially your plastic gauges. When reassembling clean the slides and their bores in the carb body with some WD40. After installing each slide and cover, take your finger and reach in through the top of the carburetor and push the slide back and let it go to see if it moves freely and isn't in a bind and that all four react the same. Install the idle mixture screws and set them at 2.5 turns out initially. Start the bike and then synch and tune the carbs.
Float Level - Roy Richards. All you need is a piece of 25 cent clear plastic hose. Hook it to the drain valve and open it. The fuel outside the bowl in the hose will seek the same level as the fuel inside the bowl. The correct level is measured down from the center of the slide. There is a mark on the side of the carb to indicate this. If it's wrong you get to take the carbs off to fix it. One turn out (air fuel mixture) tells me your float levels are too high.
Correcting a lean condition -Roy Richards
The reason a bike backfires is because it is too lean and not too rich. Your motorcycle has diff carb circuits that control diff parts of the throttle opening and RPM range. When you put the K&N in the bike it will lean out the whole range. This may help you at highway and upper RPM ranges if you really are too rich there. What I found.(and I'm at sea level but it is Hot&Humid which means my air is thin as far as the bike is concerned.) is that I had to fatten up the entire range with my Hindle. Drill out the little adjustment plugs on the pilot screws. Back them out to about 4 turns to start. (The guy with the lean condition on the supertrapp mufflers needs to do this too). This will fix the backfiring and surge or miss down low as it will fatten it up a little down there. Now take the tops off the carbs and pull out the diaphragm and needle assembly. Shim the needles up a little with a pack of little washers you can buy @ radio shack for about $1. Now you will have more mid range roll on power. You don't have to pull the carbs to do either of these things and your bike should run way better....
What is the negative effect of raising the needle too high? Runs too rich.--Sam Blumenstein #795.
Mixture is too rich, less power, lower mileage, weak response. The closer you get to right mixture, throttle response is quicker, sound of exhaust is sharper.--Don "Old Man" Smith #2
Ok I finally got my 42.5 pilots and installed them. Still wayyyyy too lean. My plugs are white as ghosts. My pilot screws are currently 3.5 turns out with the 42.5's Ok here is what not to do. While I was waiting for my 42.5's I taped up my morley air filter and went wayyy
rich. took off the tape and way lean again. Then I took a #76 drill bit and bored out my pilots (old virago trick)...that made my plugs black and sooty LOL. If I put 150's(mikuni) in the paj2's my midrange goes way too rich...off the chart rich...I currently have the 177.5's in my paj2, not sure what they are doing yet. I have sprayed wd40 on the intake boots and the bike doesnt seem to die out, so I don't think I have an intake leak, also if I did I probably would not go way rich in my midrange. So here is the current set upMains
J170 Pilots:42.5 PAJ2:177.5(mikuni) PAJ1:stock Stage7 Needles, morley air intake Float Level: 16mm (same results at 17mm)Kerker 4-2-1 w/2.5" baffle. Any ideas. Oh a side note bike only dyno's out at 90hp and compression is good.Try putting the MKNI 170's back in the paj2, see what that does, then, try taping up smaller sections of the airbox, see what that does. Honestly, if you have 42.5's in there and it's still lean, (even with the large paj2 and full box mod ) your pilot circuit is likely still not completely open. I had a set of carbs that were so bad i had to take craft wire (very small guitar string type stuff ) and push it through the circuits with intermittant sprays of cleaner to get them completely open. Look at the exploded view of the carbs to see where the pilot and bypass circuits run. i went in thru both the pilot screw and bypass holes at the front of the carbs and in thru the exit holes in the throats of the carbs. Down thru the paj1 and worked on the jet blocks too. If you can turn any of the screws in and make little to no diff. to the engine idling under 1000rpm, the pilots are not completely open and you are running on fuel sneaking around the needle jet from the main. Especially if you have the needles at or higher than 3rd clip. --steve
Low speed Carb tuning - Justin Lassy
The fuel mixture screws are indeed located behind the brass plugs. The brass plugs must be removed to access the screws. Be *very* careful about drilling out the plugs-use a drill stop. If you hit the screws with the drill bit, even for a moment, you risk running the screw down hard against its seat, destroying the screw and possibly the carb seat. Bad. The fuel mixture screws deal w/ mixture at idle and a little bit above idle. They will determine off idle throttle response and extremely low idle cruising. Turn screws in to lean the mixture out, turn them out to richen the mixture. Here are some rough guidelines to determine if you are running rich or lean at various RPM's. Examining the plugs is really the best way to get accurate results, but these guidelines will help you shoot for a direction (leaner or richer).
Idle and off idle: Lean condition: Poor off idle throttle response, idle that flutters a little after a throttle blip then slowly returns to the idle that you've set, popping back through the carbs when the throttle is blipped.
Rich condition: Off idle response may be good unless plugs are fouled from a way too rich mixture. After a throttle blip the motor will dive down below set idle and will either die if way too rich or may return to set idle if it can recover.
Setting the pilot screws - Jim Younghusband
For me, the easiest way to set the idle mixture screws, is to run the motor until warm and idle stable. Run each screw in, one at a time, until the engine stumbles, back the screw out until just rich of peak idle (idle drops again). Then run them back in to peak idle. Repeat for each carb. If your screws are out more than 3 turns, I feel the jet needs to be swapped to the next larger. Your final position should be around 2.5 turns out.
Pilot screw adjustment vs. Carb sync -Terry Campbell
The pilot screw adjustment and the carb sync are really different adjustments all together. If you had never done a carb sync it was probably good advice to do it once before fooling with the mixture/pilot screws... or anything else. The carb sync is intended to equalize the opening of the carburetor throttle plates, (this is beneficial throughout their range of operation).
The reason you see different recommended mixture/pilot screw setting in the manual for the different models is because these bikes all have different size pilot air jets, (primary ... the one on the top of the carb ... the secondary pilot air jet is the same on all models and it hides behind the slide rubber inside the carb). Air from "both" of the pilot air jets mix with gasoline from the "pilot fuel jet" to produce the mixture that you control with the mixture/pilot screw, (except when you open the throttle a little .. because there is a bypass hole .. but that is another story).
The reason you'll find the screws set differently in each carb is because at the factory, (hopefully), they set these precisely using a CO meter connected to each cylinder via the little 1/4 pipe plugs you see in the factory exhaust pipes. These differences make up for the uniqueness of each carburetor and cylinder it is attached to, (rather unavoidable .. as minute as it might be). Cranking these screws out beyond where they might have been set originally will increase the CO readings for the respective cylinder, (make it richer at idle). Even though there might be other ways to achieve your objective ... this works pretty good for adding additional fuel at off idle ... and at light, (no load ), up to about 1/8 throttle throughout your mid-range, (which hopefully you will find beneficial).
There is a limit to this benefit and if you do more to your intake etc you may find you need to do something more substantial for you light throttle fuel requirements and do something different, (like make one of the pilot air jets smaller or the pilot fuel jet larger etc). As most of these bikes have the pilot screws set on the "lean" side for emission purposes you will hopefully benefit to some extent by backing them out a little. The models with the bigger primary pilot air jets etc are going to require a little more twist to achieve a comparable mixture result, (unless you are doing the ear routine or have your own $125 JCWhitney CO meter).
Air / Fuel Mixture: The power at wide open throttle above 7000 rpm is around 12.8, not 13.8
The pilot circuit is fed into the manifolds below the throttle plate.. For many this is one of the hardest circuits to dial in for off idle or throttle response because the pilot circuit overlaps into the enrichment circuit as soon as the throttle plate is opened... the enrichment and following circuits all overlap to the next circuit and all are sensitive to velocity, not rate of air flow.I myself use the mercury stick because they give me a wide range of revving (blipping) the throttle to the point where velocity creates the vacuum needed to compress my slide springs. This gives me the best WOT right off idle... if I am tuning a bike and it's off on one of the pilots, rich/lean condition will be seen when the cylinder spikes on the mercury. Then I can make the adjustment. But still, we need to watch the tack because although we get it all equal doesn't mean its right... they can all be too rich/lean... at quick blip, the needle should rise up then drop to the set rpm, not float or hang or fall below the set rpm. And like I said in past posts, don't be surprised if one pilot is .5 turns and another is 3 turns, this is normal... only way they will all be the same is if the valves are tuned.-Paul
Carb Rebuild
Clean all four carbs?, did you disassemble the 4 carbs from the side rails or just broke them down to tow pairs? Did you remove All the jets?? When you re-assembled them did you make sure the side plates were tight? you first mistake was not syncing the carbs first!!, every time you that carbs off and or apart the sync gets thrown off, and depending how much pressure was used to get them back in the boots can a will throw them off even more, your best bet now is remove the carbs, flip them over and see how the throttle plates are relative to the bores, I'll bet you'll find them all out of adjustment, some or not all, of them will be open too much, adjust all of them back down to almost fully closed, then re-install, warm up engine and sync the carbs FIRST THING!!
stock is 152.5 mikuni jets.. you're running dyno jets. 175 is very rich for a 4-2 system... the dyno jets instructions will get you in the ball park. those instructions are as old as the bike, the new pipes aren't even listed and there's been a significant change to the needle spacer that dynojet don't know about... what I would do with stg 7 marks pipe is start out on the 2 clip (depending on the bike year), in many cases 2 is too lean and 3 too rich.. So I came up with the needle shim kits (and sold a lot of them)... these shims will give you a true 1/2 clip... use the stock mains... if too lean go to the 155 mains... set the floats 17mm if you want maximum power you need to adjust each circuit for a smooth transition through out the range.. this is where you will get power... the engine should accept full throttle from any rpm. at wide open throttle it should tach out in a heart beat. don't tune for big dyno numbers... tune for a good agressive curve with no dips.
It depends on which 165 main jets you have. I would bet they are 165 dynojet jets which are very similar in actual size to the Mikuni 152.5 main jets (they are rated differently). You can id them by looking into the end of the jet and see if the hole is "flush" to the jet or if there is a bit of "countersink" to them. Either way, the 152.5 works well 99% of the time with most configurations (stock or header) unless you have slip-ons which then smaller jets tend to work better.
Muscle Jet Kit:
New "Panel Filter" (K&N or Air Hog) - installed into your airbox lid
Air Correctors
Lighter Springs
Drill bit (for the slides)
Large Selection of jets (6 sizes)
The stock needles work just fine even with this setup and produce stage seven power with V-boost still fully intact. Mileage is in the 40's. HP is in the 120's. Torque is in the low 80's high 70's. Easy to install and tune in (if you can take carbs off and have the ability to sync them).
Factory Pro, CV Carb Tuning
Follow steps in order....First, dial in:
1. Top end (full throttle / 7.5k to redline -
Best Main Jet must be selected before starting step 2 (needle height)!
Select Best Main Jet
To get the best, most even top end power (full throttle/after 7500 rpm), select the main jet that produces the highest top speed / pulls hardest at high rpm.
If the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. Install a smaller main jet and retest until you find the main jet that pulls the hardest at high rpm when fully warmed up. This must be done first - before moving on to the other tuning ranges.
If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small.
In order to properly tune the midrange and low rpm carburetion, THE MAIN JET MUST FIRST BE PROPERLY SELECTED after 10 to 15 minutes of hard use!
Do not pay too much attention to the low-end richness when you are changing main jets - you still need to be using the main jets that produce the best power at high rpm. You will deal with the low-end / cruise later - after step 2.
2. Midrange (full throttle /5k-7k)
Step 1 (Best Main Jet) must be selected before starting step 2!
Select best needle clip position
To get the best power at full throttle / 5k-7k rpm, adjust the needle height, after you have already selected the best main jet.
If the engine pulls better or is smoother at full throttle/5k-7k in a full throttle roll-on starting at <3k when cool but soft and/or rough when at full operating temperature, it is too rich in the midrange and the needle should be lowered.
If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k.
If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set.
Do not pay too much attention to the low-end richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle / 5k-7k power in conjunction with the main jets (Step 1) that produce the best power at high rpm. You will deal with the low-end / cruise next.
3. Low end (full throttle / 2k-3k)
Step 1 (Best Main Jet) and Step 2 (needle height) must be selected before starting step 3!
Float height (AKA fuel level & how to..)
To get best low-end power, set float height (fuel level) so that the engine will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum.
Float heights, unless otherwise specified in the installation guide, are measured from the "gasket surface" of the carb body to the highest part of the top of the float - with the float tang touching but not compressing the float valve spring.
If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm, that gets worse as the engine heats up, lower the fuel level by resetting the float height 1mm greater (if the original was 13mm - go to 14mm). This will lower the fuel level, making full throttle / 2k-3k rpm leaner.
If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.
Example: change float height from 15mm to 14mm to richen up that area.
REMEMBER, since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting.
Warning: If the engine is left with the fuel level too high,, the engine may foul plugs on the street and will be "soft" and boggy at part throttle operation. Adjust Floats to raise/ lower the Fuel Level.
Base settings are usually given if a particular application has a history of fuel level criticalness. The Fuel level height in the float bowl affects full throttle/low rpm and, also, richness or leanness at cruise/low rpm.
Reference: a bike that runs cleanly at small throttle openings when cold, but starts to show signs of richness as it heats up to full operating temperature, will usually be leaned out enough to be correct if the fuel level is LOWERED 1mm. Check out and RESET all: Suzuki (all), Yamaha (all) and Kawasaki (if low speed problems occur). Needless to say, FUEL LEVEL IS EXTREMELY IMPORTANT!!!
If there are low-end richness problems, even after lowering the fuel level much more than 1.5mm from our initial settings, check for needle wear and needle jet (part of the emulsion tube). See Worn Needle and Worn Needle Jet diagram. It is VERY common for the brass needle jets (in the top of the "emulsion tube") in 36mm, 38mm and 40mm Mikuni CV carbs to wear out in as little as 5,000 miles. Check them for "oblong" wear - the needle jet orifice starts out round! Factory Pro produces stock replacement needle jets / emulsion tubes for 36mm and 38mm Mikuni carbs.
4. Idle and low rpm cruise
Fuel Screw setting (AKA mixture screws)
There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil. Cap removal details. Newer Honda carbs have no caps, but use a special "D" shaped driver, usually supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation. (pj tuning information)
Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
NOTE: A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
NOTE: A lean problem gets better as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!
Carb Kit Design is a combination of science, art, intuition and and at times, a fair dose of wizardry. There is no dyno that "tells" one how to assemble or modify the carb to deliver proper power and response.
Perfect Carb Kit TUNING requires patience and perseverance and "reasonable" feel to feel the changes - of which - most motorcycle riders have a good ability to do.
When a dyno "operator" says he/she has to ride the bike after dyno tuning to do the final tune for cruise smoothness - that's what they are doing. Avoid any dyno operator who says that they don't have to do that!!!
The only dyno that I know of that will duplicate and visually display the engine smoothness is the EC997 dyno (yes, I know, we make it) - that's one reason why, if you can, you'd like to use one for tuning - a smoother engine IS getting the best mixture. Other dynos claim to "tune to an "A/F Ratio" - probably the biggest marketing scheme in the dyno industry at this time - and they never can equal the quality of tune as designed -These tuning kits have been thoroughly tested to ensure easy, trouble-free, optimized performance.
Please note: If you have installed the kit and gone through the optional screw settings, clip positions and main jets, and still have a persistent flat spot/problem, we ask you to call us. Unique engine / exhaust / filter / altitude / temperature combinations may require individualized setups. We are here to help. The information gained to your solution will be installed in our computerized reference database. PLEASE CALL!
We (Factory Pro) ask that upon completion of installation and tuning, that you call us with specifications of your installation, (pipe brand, filters, advancer, altitude, humidity, temperature and final carb settings) to be entered in our TUNING DATABASE. The database allows us to include the "most used" jet sizes and setup specifications in every kit. Use (415) 491-5920, (800) 869-0497 or fax (415) 492-8803.
Jets / Jetting
Pilot jet 37.3
Pilot air jet1 is 90
Pilot air jet2 is 170
Main jets have little or nothing to do with fuel mileage unless you are riding above 7500 rpm all of the time.
Fuel mileage is mainly a result of..... in order of importance
# 1 Float bowl fuel level...17mm...never over or higher than 16.5 mm
#2 Mixture screw settings... As lean as possible. Set up your carbs...then take a ride and adjusting each carb one at a time. With the engine at operating temperature Start with one carb and turn in the mixture screw a very very small amount at a time ....turn it in a hair..then ride it . Turn it in some more then ride on ....keep doing this until the carb starts to spit back when you accelerate or take off from a stop...then back out the screw a bit at a time till it stops spitting ....When done go to the next carb ....it takes a while to do this . I just carried a small screw driver in my pocket for a few rides and kept working with the screws. This is how we get over 40 mpg. When it is right the bike will be cold natured to start even in the middle of Summer and will idle smooth when warm. I always just smile when someone tells me how well their bike is in tune because it does not need the choke to start.
#3 Needle setting or depth and the condition of the needle and its receiving jet. Stock is stock....If your needles are adjustable then if ....White in color retainer ...1.5 to 2nd notch...beige in color 2.5 to 3. is a good setting starting point with an open exhaust .
#4 Fresh spark plugs....use the stock plugs and change them at least every other oil change....I do mine every oil change ...They are cheap and the bike runs crisp
# 5 a good and perfect valve adjustment helps a lot too if they are out....it also makes tuning easier if all the cylinders are making equal pressure as a result of valve adjustment
As you can see....Main jets are not in the picture. If your main are Mikuni jets ....160 is way too big for your set up ....but if they are DynoJets they are just about right on.
With this set up you too can get over 40 mpg cruising at 80 mph + My bike with stg 7 got an average of between 130 to 140 miles to the red light all the time. Even hammering on it all the time in the mountains got well over a 100 miles to the light It is a matter of keeping it in tune.
Highway steady cruise should be above 40mpg.. mid-range is where we do most of our riding and the needle position in the needle jet is important considering that both mid range and top end mix is delivered through the needle jet where the jet needle meters the flow into the venturi for the final mix.. if your using aftermarket needles adjust the clip to get a little more needle into the needle jet--paul
The mercury sticks are vacuum sensitive and basically designed to synchronize the 4 carb butterflies. With butterflies varying in seated position you will see a different vacuum signal from each engine cylinder. By equalizing the throttle blade openings (synchronizing carbs) you will see the vacuum signal equalize so that all carbs are as equal as possible through the throttle range. This means each cylinder sees, as close as practicable, the same amount of throttle at all openings. Which in turn sees each cylinder having the needle the same position in jet etc. throughout the throttle opening range. Basically this means each cylinder has the same fuel curve as the others. That's the aim of synchronizing the carbs. It's a mechanical adjustment so equality of carb operation to each cylinder occurs.
The idle screws are basically pilot or idle circuit fuel curve adjusters. The idle circuit caters for idle through to about 1/2 throttle or so when the fuel curve is influenced more by the needle and main jet. I'm not an expert on these carbs so others can be more specific but from my experience the idle screws will only have an effect on vacuum as you close them down too much or open them up too much causing excessively lean or rich mixtures respectively. You don't really need a vacuum gauge to measure this; it is very obvious in that the bike starts running rougher when you go too far with any of the individual pilot screws. As many like Paul and Don have said before, you need to turn each screw in fully till the engine stumbles and roughens up then back out till it stumbles with too rich a mixture and go back in till you have the smoothest possible running. Do this with each cylinder screw in turn and don't panic if some of the screws have a lesser effect as you go in or out. Just try to end up with the smoothest idle and blipping the throttle should leave the bike with the tach needle dropping back down to a clean idle rather than dropping below idle speed and rolling back up (too rich) or hanging up after blipping the throttle and slowly returning to a good idle (too lean). The only other way to do this is to have an accurate A/F ratio gauge setup in each exhaust header. We do this on the engine dyno on extreme performance and race engines every day.
As I said I'm not a Vmax carb specialist but doing this sort of tuning with the carbs often enough you will get used to where the bike runs best. Unfortunately there are many more variables effecting this like how well the valves are set (effects cylinder vacuum), even compressions on cylinders, condition of carbs in general like clean idle circuits, correct float levels, coasting enrichment assembly operation, condition of carb diagrams, condition of needles and main jets (they wear into each other over time) and more.
We need a decent fuel injection system frankly. Set it and forget it, although for the big engines I do like the 39mm flatslides. They are more temperamental than the stock carbs and need constant adjusting (I like doing this anyway) but because they are fully mechanical they respond exactly to changes unless they have too much internal wear.--Sam Blumenstein #795
I'm having idle problems with my #3 carb. I get a random idle if I completely open the mixture screw. Everywhere else, no idle. Every other circuit is fine though. I can accelerate fine everywhere else...it's just steady cruise or small throttle below 4000 rpms. Before, I had the screw set to about 4.5 to 5 turns before the cylinder idle. I've replaced the sparkplug, checked ignition and it's firing perfectly, compression is about 180 psi. I did the shotgun and that didn't help at all. Float level is spot on. I'm going to check the enrichening plunger, maybe it's stuck open. Other than that, going to break open float bowl and remove jet block. Could be plugged pilot fuel jet. Maybe a piece of gasket is blocking one of those holes.
Answer to problem turned out to be: Blocked purge jet.--Eric h
I'll check that again. I did as you suggested before, use straw and blow in all 3 holes and listen for air. Could be blocked now I guess. You said once before that carb cleaner doesn't work for those right? To use small wire? What gauge of wire did you use? It's still amazing to me that those small purge jets cause so much trouble.
Do not know ..gage....small wire is found here at Craft store....The hole behind the diaphragm on left side is the one that gives the most trouble....if blocked completely there will be a small amount of fuel when you pull the cover off. Remember you are dealing with a carburetor for a high performance 300 cc motor. -Eric h
I'm writing an article for the next Vboost but thought I would share some findings here first:
Morley Pros:
- Velocity stacks richen you up everywhere, mask some low-end carburetion problems
- Cheaper product ($200)
- works well with stock main jets if using DJ needles
- also works well with stock needles
- works best with stock vboost
- Vmax seems to like the airbox and velocity stacks
- change of humidity/temp isn't noticeable, no jetting changes necessary for cooler temps
Morley Cons:
- Velocity stacks richen you up everywhere
- more work to tune low end carburetion (I think bigger PAJ1 would help, didn't have the jet selection to try)
- bigger mains (Mikuni 162.5's in my case) are needed with stock non-adjustable needles
- open vboost makes low end richness problem worse
Stage 7 Pros:
- Works with stock or open vboost
- easier to tune low-end
- works well with stock main jets
- intake noise gives me a chubby
- works best with open vboost
Stage 7 Cons:
- Expensive ($300 - $450 depending on vendor)
- more filters to clean/oil
- supplied puke bottle is cheesy looking
- you can smell the blow-by crank gases
- more temperamental to changes in weather --Mark Milne #1098
this thing is killing one carb back ride side as you sit on the bike is spitting up and wont sync i had the carbs apart and cleaned everything i just dont get it and i'm thinking then fuel is ok but way out of sync I think i'm done with this no fuel injection crap i have done this before with no problems stage 7 with 165 jets in and needles set on 3rd clip it almost souns like a miss but the spark plugs are new today'
what yr. ? are you sure you have all the intake connections seated and tight ? how about the slide diaphram, you didn't happen to loose one of the little springs that are on the synch linkages ? if you have the vboost hardware in and can close it , it will be easier to work out.
i have seen something similar to this before after extensive carb work and the synch was very far off. sometimes you need to use the idle speed set screw to keep it running until you can get the synch closer. just to cover the basics, the left front carb is the control, it is non-adjustable. the left rear is synched to match the left front. then without regard for the left
side levels, the right front and rear are matched to one another using the rear synch screw on that side. then the right side is matched to the left with the front synch screw on that side. but
you've done that before and now and still have problems. spitting back up through the carbs is a lean issue that could be that that cylinder is way out of synch, a vacuum leak or a blocked main air jet (top of carb), problem at diaphram or paj2 or a clog in the pfj or the bypass circuits between it and the pilot screws and / or the outlets into the venturi's. sorry this doesn't seem to track it down much but it gives you places to look.-Steve
Needle Adjustment
Do 2.75 clips from the blunt end of the needle. Do the needle test as Don suggested. Here it is:
1) 4th gear, 4K RPMS: WOT until 6K RPMS; let off throttle and if it speeds up, running rich and lower the needle.
2) 4th gear, 4K RPMS: WOT thru 6K RPMS; at 6K, give it some choke; If it speeds up, running lean and raise the needle. If neither condition happens, needle position is fine.
While in 4th gear rev to 4k. Open her up to 6k. Turn choke on and do the same thing. Did power get better or worse? If it got better...too lean raise needle. Worse too rich lower needle.
Carb Tuning
well, Dale is no different than any other vendor that sells products. Only thing that bothers me is his lame jet kit. 4 washer, 4 big main jets and a filter for how much? This kit will richen the hell out of the mix. Rich is smooth and most buy into it with a pipe thinking their
bikes run great. I removed more DW power kits then I can remember and the owners were freaked about how much power then gained. The dyno jet stage one isn't bad as far as needles, spring, and slide drilling. One can cure a rich condition by leaving the main jet stock and adjust the needle to meter the mix to the lean side. There is no majic top end running on mains only, the main jet pilots the fuel to the needle jet but the jet needle controls how much mix enters the venturi for final air mixture. So what are we doing when we lower the main jet but increase the needle height? The main jet will control the flow at top end but mid-range will be rich. So best to leave the main stock, get a set of adjustable needles and pilot the flow from there. Another thing we can do is.....If you have a post 93 max with fat needle spacer and its rich, find a set of pre 93 needle spacers and lean it out. Vise versa with the lean
condition on a older max. Its all about tuning. Stage 7 is the best way to get a fine tune but there is nothing wrong with the stock airbox tuning either. The bike is set from the factory for a wide range of temps and altitute conditions. It will run and for most it will run good but, what bad if we dont know good. We recommended so tuning for someone at 5000 feet. PAJ#1 went from #90 to #100, needle was adjusted with a smaller spacer and the PAJ#2 was increased. This person claims his bike runs like a bat out of hell. I believe him, jetting should be adjusted along with the shift lever and brake pedal-paul
Before changing anything I would take your carbs off and see what you have. Check the size of the main jets (152.5), the pilot air jet #1 at the top of each carb (90) and pilot air jet #2 behind the slides (170). It's very likely that the previous owner just dropped in bigger jets all around thinking that more fuel equals more power. Check your float levels too. Make sure all four read the same....either 16 or 17 mm. Here are a couple of links to get you started in the inards of Vmax carbs:
http://vmax.lvlhead.com/tips/carb/walsh/walshcarbs.htm
http://vmax.lvlhead.com/tips/shotgun.htm
http://imageevent.com/wforest/carbswhatamess;jsessionid=qx8h4ccve2.zebra_s
Mark Milne #1080
Determining Rich / Lean Conditions
your too rich. Even the 150's are rich for your altitude...152.5's make it worse especially past 7500 rpms. The general rule is to decrease main jet size by 1% for every 1000 feet of elevation. 152.5's are great jets for sea level but not for you. So, I'd put 145 mains in. Then, I'd make sure your floats are all set to 17 mm. Some guys in your area have messed with the pilot air and fuel jets but I don't think it's necessary unless you can't get a good idle mixture by using the mixture screws. On your '85, how was the airbox modified? Try removing your "Y" and see how that does too. After your main and floats are correct, do the following test for your needles.
1) 4th gear, 4K RPMS: wide open throttle until 6K RPMS; let off throttle and if it speeds up, running rich and lower the needle.
2) 4th gear, 4K RPMS: WOT thru 6K RPMS; at 6K, give it some choke; If it speeds up, running lean and raise the needle.
If neither condition happens, needle position is fine. If you need to lean the needle your outta luck since stock needles aren't adjustable. I'd look at getting stock Canadian Vmax needles or DJ stage 1 needles. These are adjustable. You could use Factory Pro but they're titanium and will wear out your needle jets over time. Valve adjustment will help out too. I noticed the biggest difference when i adjusted my valves. Make sure all the intakes are the same....same with the exhaust valves. --Mark Milne #1080
STAGE 7
Use the pauls pea shooter method next time you start the bike. turn your pilot screws out 2 full turns. choke on start the bike, squirt sea foam in the choke vent at the top of carb, this will be the hole above the choke valve. do this while its running, no reving but keep it around 1500rpm.. now, once bike is warmed up, choke is off, squirt sea foam in the Pilot air jet #1.. this is the removeable jet at the top.. slight revs will allow the engines vacuum to draw the sea foam down the air circuit to clear it up.. if you should get sea foam into the carb throat dont worry about it, you will have some smoke out the exhaust is all but it wont hurt anything.. once done set the screws back in 2 whole turn where you had them. you dont want to use compressed air. compressed air will force and dirt into the circuit and clog things worse and once the enrichment is plugged, forget the address... 175 is too big, use the mikuni 150 or 152.5. The main jet gives good power to the low to mid range? you are misinformed. Your pilot screws and needles are adjustable to calibrate the best mix in these ranges.. these 2 ciruits are the most crucial and its not as simple as dropping in different mains to get dial them in. I suspect the bike has yet to see its full potential. Follow instructions above, if that helps close the boost and synchronize the carbs.. once that is done open the boost back up.
Once you got it going let me know. I will dial you in the rest of the way. Things to document, what needle clip, what PAJ#2 under the slide? -Paul
Check the air filter, see that you have Mikuni 170 jets at paj2,synch the carbs and adjust the pilot screws as close to 2.5 turns out or under as you can get them without spitting back thru the carbs or sluggish off idle. -Yarddog
Took my bike (2000) out for the third ride of the season and is was running great as it was on the last two rides. All of a sudden, it started to miss or sputter between 4 and 6000 rpm. As soon as v-boost kicked it, it took off like a rocket. Took it out today for a little ride, and it was doing same thing.
your mission today is to remove the airbox cover to get a visual on the carb slides.. sounds like one or 2 are hanging up.. -Paul
Carburetors Removal
you must take off the carbs. It's easiest when you break them into pairs. Once the carbs are off the bike, remove small e-clip holding choke linkage rod onto carb #4. Then, remove e-clip plus washer from sync rod. Then remove front and rear bracket (4 screws each). Finally, disconnect "T" fuel hose that links left and ride sides. reak open the culprit carb bowl and the other one that's a part of that pair. Flip the pair upside down and set on level surface. Then use the picture I included and make sure the 13 mm carb distance matches the 16 mm. Using a digital caliper makes it pretty easy. hen you put the carb back on, you'll have to sync your carbs. et us know how you come out. -Mark, #1098
i put a new ufo 4 into2 exhaust on my 85 stage 7 max, i had a 4-2-1 kerker on it but with only a 1-1/2" baffle.. it ran strong and fast but the pipe is worse for wear and needed to be replaced, redone,(ill put it on my 98 when im finished)..anyways, i was hopin to get some suggestions as to my carb stup to gain some of the power back ..i have 175 mains in now and i believe the needles are set at 3rd clip down from blunt end.. i seem to have decent power up UNTIL 4000 rpm then i lose all power, it will accelerate but with no pull or excitement, nowhere close to my kerker, i know the kerker is better for power BUT there should not be this much of a difference.. im in ontario canada so elevation is about 300 ft or so..at around 7or 8000 rpm it picks up power again but not a LOT, is my major problem in my needle height?
I have a 98 full stg7,4-2 Marks, and my mid rang is on par with a stock Max, but I spend little time there. At 5 grand it starts pulling hard, and at 7 grand to 10 grand I'm glad to have a stepped seat as the tach lunges forward on a second hit, and my fingers stretch. After much experimenting I ended up with using DJ-175 mains (no, its not rich), and dJ needles on top (leanest) clip. Also, if mileage went to crap, another indicator of rich. When I went from Supertrapps to a full header it richened the mix, and my clip was on the same place as yours, and raising it to the top corrected it. And the needle position DOES affect mid range and top end. --Randy3539
Some run stage 7, open boost...170's or DJ190's. Some run stock vboost with 170's and 190's. Some run tboost with 170's or 190's. Try it with the 170's. If running rich at off-idle or at 4-5000 rpms at small throttle angles then increase the PAJ2.--Mark#1098
I purchased the Morgan Carbtune and received it about two weeks ago. Just finished using it to sync my new EFI throttlebodies on Sunday. What a great and easy to use tool. I sync the #2 to #4 and then #1 to #3 and then 2/4 to 1/3 and really worked well.--RickRash#1283
The tubes are connected to the spigots, engine running and idle set, what does the gauge reading mean?
1. Use a light blipping of the throttle to see where the four SS rods settle.
2. If you have not synchronized for awhile they will probably be slightly uneven. The bigger the variation the more out of sync the carbs are with each other.
3. To sync the carbs, start with the back left carb (#1), (NOTE: the front left carb (#2) is the Master Carb on the Vmax, and all others have to be adjusted to match it) making adjustments to its set screw to the point where the rods are the most even. At that point you will move to the right side, do the same for carb #3 (back right) and carb #4 (front right) and then move over to the left side carbs, doing one again. Slightly blip the throttle after each adjustment to see the affect. The left side and right side carbs are linked together, so it may take a number of time, moving back and forth to each side.
4. The carbs are very sensitive to adjustment. Adjust one carb at a time and then check the reading. Give the gauge a few seconds to settle after each adjustment. It is generally necessary to gently blip the throttle to seat the carb that has jut been adjusted.
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