Recommended carb jetting/setup

[dodgediesel59]

Hey guys i am getting towards the end of my frame up resto on my 86 and was curious what jetting and other mods i need to do to make this perform. The bike as i got it was bone stock. Now the vboost is going to be on all the time but am leaving butterflies in so i can sync the carbs still. I am going to run a marks 4-2-1 with 14" can and get a morleys air box lid. Also put COPS on the bike, but doubt that should affect anything with carbs. Just looking for a close setup so just maybe i dont have to pull them off again... Thanks guys!

 

[SpecOps13]

I tried to figure this in my head but there's too many factors different from my Kerker 4-1. You are running stage 7 with free'd up intake using Sean's Lid, also Mark's Exhaust. I really want to know what you think of Mark's 4-1. Once you have a chance to ride it. I may replace my Kerker with the same. I see that your question has been up for a while with no answer so I'll bounce it to get more attention.


Good Luck.....

 

[[email protected]]

Hard to say for sure, each bike is different. Most bikes like to go a size or two leaner on the mains with a full header. Some guys say its fine stock.

Most bikes like a little shim on the needle too when you go to a full header, but running vboost open all the time may richen the midrange and eliminate the need for it.

So, if it were me, I'd try 150 mains(assuming your elevation is around 1000'ASL) and no shims and go from there.

More of a guess, I'm no guru.

 

[KJShover]

Like as mentioned, some bikes get by just fine with a simple shim and a few turns of the a/f screws.

I'm at 440' above sea level. I'm running just fine, 40mpg with:

Morley kit
Stg 7 needles, clip at 3 from the top
150 mains
a/f's (vary from carb to carb) average about 3 out.

 

[dodgediesel59]

Thanks for the advice guys! I think i might just try to run the marks without the lid and jet kit and do shims and screws to keep things cheap for now. I have a ton of money stuck in it from all the odds and ends that keep getting me on top of rebuilding the trans. What size shims you guys running? Spec my buddy has the same system on his vmax and i absolutely love it. It has one of the best sounds but its hard to comment on power increases as his bike has a pcw engine turning out about 170 horse at the rear wheels. I will get some pictures up soon of the slow painful process.

 

[06VMAXIMUS]

Welcome to the forum! Danny turned me on to his setup which I used on mine: check your carb float levels and adjust if needed (mine were way off), turn mixture screws out (from closed) to 3 or 3&1/2, shim needles to .038-.040. With the Marks exhaust, this should get you real close. Perfection comes with Morleys kit and a good afternoon of dyno session (from what I understand). Bob EDIT: I have no clue how these settings will work with your boost butterflies open all the time.

 

[Rusty McNeil]

Not sure if you meant your running seans air box by itslef or his jetting for it too??

Here's what I got

Stock motor; 44,000 miles
UFO 4-2 Exhaust; similair to Marks without the crossover

I ditched the controls and motor on the Vboost but left the Vboost butterflies and cable in place so it could be properly synched, I use a throttle cable "stop screw" to hold the Vboost open..

Running carbs with
paj 1 & 2 stock
Two coils cut out of the slide springs
About .015 worth of shims under the stock needles
The top horizontal "plane" of the the air box Y is trimmed completely off.

I ran 165 dynojet mains for a long time and was pleased with it, it would out run most of my buddies maxes this way.
I rejetted it to mikuni 145's when I took it to Utah for several months (Elevation 5000-9000 ft.) so it run ok up there.

When I got back to Home, Houston, Elevation 20 ft., I rode it once with the 145's in it which I was sure were too lean for this altitide and discovered it ran Fan-fucking-tastic, like never before, it was an extremely noticeable improvement... it "loved the lean"....Still too lean for comfort tho so I went up to mikuni 147.5's last time I went through the carbs and it's better than ever....I run a wideband a/f monitor so am not worried about it going to lean on me..it's definitely not...

Most maxes are way fat on the jetting even stock in my opinion...

Someone else mentioned float levels, they were right. Float levels can really effect the performance, mine were way off too...I set them up just slightly low..

Factory Tuning company has an EXCELLENT free tutorial white paper on how to tune carbs in general and it goes into the float levels and how they affect midrange tuning to a good degree

 

[max03]

I live in upstate NY and wanna go through my carbs, i've had them off the bike to change the mains, but really wanna change the pilot jets. They look like a real pain in the ass to take apart to do this! Right now i have the stock 152.5 mains in i wanna go down a size or two. What size is recommended for the pilot jet? The bike is all stock with a 4 into 2 holeshot performance exhaust. I tried the 155 mains recommended but ran sluggish so thinking 150 or 147.5

 

[SpecOps13]

max03: I had 155's and 1 heat range hotter spark plugs in my 89 when I bought it... Installed 152.5's and it was still running way too rich even with the hotter plugs. I now have 147.5's in with standard spark plugs and the jury is still out. I'm at sea level, stock needles are shimmed 0.032, AF Screws are 3-1/4 turns out and all other jets in the carb are stock. My Exhaust is Kerker 4-1 with a 2" core... Stock air box with K&N which really makes no difference. 34k miles


Hope this is of some help to you in some way...

 

[maleko89]

I live in upstate NY and wanna go through my carbs, i've had them off the bike to change the mains, but really wanna change the pilot jets. They look like a real pain in the ass to take apart to do this! Right now i have the stock 152.5 mains in i wanna go down a size or two. What size is recommended for the pilot jet? The bike is all stock with a 4 into 2 holeshot performance exhaust. I tried the 155 mains recommended but ran sluggish so thinking 150 or 147.5

No need to change the pilots really. You can usually get the pilot tuning your want by changing either the pilot air jets #1 or #2. Pilots are 37.5...if you want to change I'd say go to 40's at most.

 

[max03]

max03: I had 155's and 1 heat range hotter spark plugs in my 89 when I bought it... Installed 152.5's and it was still running way too rich even with the hotter plugs. I now have 147.5's in with standard spark plugs and the jury is still out. I'm at sea level, stock needles are shimmed 0.032, AF Screws are 3-1/4 turns out and all other jets in the carb are stock. My Exhaust is Kerker 4-1 with a 2" core... Stock air box with K&N which really makes no difference. 34k miles


Hope this is of some help to you in some way...

It does help i was kinda worried about how far to jet it down, in previous bikes owned whenever i put an aftermarket pipe on i always jetted up one jet size. But when i went up one on my vmax i was shocked that it ran lazy. The bike woke back up with the stock 152.5 in it and i know it will really wake up one to two sizes smaller. The pilot jet has me stumped alittle, i have my mixture screws turned out around 3 turns i was told the vmax is lean from the factory on the pilot jet does anyone go up or down with this jet? Also how hard is it to break these carbs down to pull the bowls off? i changed the mains through the brass plug on the bottom so didn't need to break the carbs down. I also wanna check the float height what is the recommended setting?

 

[SpecOps13]

There is an easy way to check the float levels. I just haven't fully figured it out yet. There are external markings or part of the casting. So by using a clear tube on the drain, you can verify the levels with the carbs on the bike and the bike level. That's my understanding anyway. Somebody will correct me...:biglaugh:


Disassembly of the carbs depends on how much Rocket Scientist is in you...:confused2:Easy for some scary to others...

Good Luck,
Dave

 

[dannymax]

I've had good luck with Mark's 4-2, a needle shim of .038" and backing the A/F screws out to 3 1/4. My '99 pulled 117.1 on the dyno @ PCW with this set-up....stock other than COP's.

Where in upstate NY are you, I'm southeast of Albany near the Mass border.

Also, NaughtyG did a great series on carb dis-assembly, cleaning and re-assembly.

http://www.vmaxforum.net/showthread.php?t=5830
http://www.vmaxforum.net/showthread.php?t=5831
http://www.vmaxforum.net/showthread.php?t=5832
http://www.vmaxforum.net/showthread.php?t=5833
http://www.vmaxforum.net/showthread.php?t=5834

 

[dannymax]

There is an easy way to check the float levels. I just haven't fully figured it out yet. There are external markings or part of the casting. So by using a clear tube on the drain, you can verify the levels with the carbs on the bike and the bike level. That's my understanding anyway. Somebody will correct me...:biglaugh:


Disassembly of the carbs depends on how much Rocket Scientist is in you...:confused2:Easy for some scary to others...

Good Luck,
Dave

That is correct Dave, facing the carbs there is a line on the left side of the carb body just behind, and about on the centerline of, the diaphram cover. You want your fuel level 15mm - 17mm below this line.

That is just for checking purposes as it's nearly impossible to do any float adjustments with the carbs on the bike. I prefer doing all that on the bench.

 

[gamorg02]

danny i was wondering the same ething, where in 'upstate'?

 

[max03]

Seneca Falls, Right between Rochester and Syracuse

 

[gamorg02]

i played rugby states in that neck of the woods. girlfriend went to ithaca, i'm originally from whitesboro (utica)

 

[max03]

i played rugby states in that neck of the woods. girlfriend went to ithaca, i'm originally from whitesboro (utica)

Ithaca is at the south end of cayuga lake Seneca Falls is at the northern end love riding down there in the summer

 

[gamorg02]

yea unfortunately moved away from 'home' before i got into bikes. ridden a few times back home on the 'max tho.

 

[dannymax]

Seneca Falls, Right between Rochester and Syracuse

Nice riding over your way....just a skip down to 'The Glen'