Hey everyone this is my first post. Im in south Florida and I just picked up an 89 Vmax that is a little rough. The bike is complete and starts right up and runs but not on all the cylinders. The odometer says 6000 miles but I seriously doubt it, although it does looks like it sat outside neglected for a while. The guy I bought it off of I'm sure just flipped it for a profit and didn't have a have any real information. I rode the bike home which felt like I was riding a 250cc and immediately began getting into it. At first look the tires are newer and the battery is brand new. The carbs definitely showed signs of having been gone through, (mismatched screws, messed up heads). The exhaust is aftermarket ( unknown which one) with one side muffler. The airbox is gone and has individual K&N pod filters. I drained the oil and it stunk of gas. I tested the coils and found that two were bad. Also the spark plug wires barely in the coils at all. I've been reading a lot of posts and decided instead of getting factory coils I would go with COPS. I have a set coming and also ordered a Ignitech from Sean Morley. I figured this would be a safe way to guarantee the ignition system was up to speed. I pulled the carbs off and so far only opened up one. Once disassembled I noticed the main jet was replaced with a 170. This carb has (2) 170 jets, (1) 90 and (1) 37.5. Seems a little big to me, but with the bike being of unknown origin just curious what everyone thinks of the jetting with the exhaust and K&N pods. Thanks guys.
New owner of an 89 VMAX
- Thread starter Vinny9744
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Where in so. FL?
Looks like you're the owner of a 4/1 Stage 7 jet kit bike, the '89 has the early ignition. Nothing the matter w/it until it goes-bad. The Stage 7 Dynojet #'s are different from factory Mikuni #'s. The DJ #'s are higher-numerically for the same diameter.
The pilot jets are the 37.5 'shorty' jets in the jet block. Be sure that you replace the rubber plugs in all the screw-in jet holes in each jet block, or the bike won't run properly. Two plugs in the left and middle holes, they're different & the bigger one goes in the middle.
You have the big rubber hose from the oil filler cap to a small plastic canister, and hoses from the 4 pod air filters?
This carb has (2) 170 jets : not sure what you mean by this? The main jet is in the end of the jet block (jet block: part #32, fiche, below). There is only one main jet per carb. Do you mean, "the two carbs I opened have 170 main jets?"
I'd remove those 170 main jets and replace them with 147.5 Mikuni factory jets (two sizes smaller than stock Mikuni 152.5) . I suspect you are running about four jet sizes too-rich! A Mikuni jumps 2-1/2 per jet size while the Dynojet jumps 2 per jet size. A Mikuni 152.5 OEM-spec VMax USA main jet = 162 Dynojet main jet.
Part #46:
Jet, Main (Mikuni 152.5) (3G2-14231-
3G2-14231-81-A0
152.5 is the OEM Mikuni jet size
https://www.ronayers.com/oemparts/a/yam/50042e28f8700209bc78a2ba/carburetor
Here is a Dynojet to Mikuni chart (thanks to CaptainKyle ([email protected]), a good source of parts and work, as are other members on here:
https://yamaha-enduros.com/index.php/workshop/carb-jet-conversion-chart
Looks like you're the owner of a 4/1 Stage 7 jet kit bike, the '89 has the early ignition. Nothing the matter w/it until it goes-bad. The Stage 7 Dynojet #'s are different from factory Mikuni #'s. The DJ #'s are higher-numerically for the same diameter.
The pilot jets are the 37.5 'shorty' jets in the jet block. Be sure that you replace the rubber plugs in all the screw-in jet holes in each jet block, or the bike won't run properly. Two plugs in the left and middle holes, they're different & the bigger one goes in the middle.
You have the big rubber hose from the oil filler cap to a small plastic canister, and hoses from the 4 pod air filters?
This carb has (2) 170 jets : not sure what you mean by this? The main jet is in the end of the jet block (jet block: part #32, fiche, below). There is only one main jet per carb. Do you mean, "the two carbs I opened have 170 main jets?"
I'd remove those 170 main jets and replace them with 147.5 Mikuni factory jets (two sizes smaller than stock Mikuni 152.5) . I suspect you are running about four jet sizes too-rich! A Mikuni jumps 2-1/2 per jet size while the Dynojet jumps 2 per jet size. A Mikuni 152.5 OEM-spec VMax USA main jet = 162 Dynojet main jet.
Part #46:
Jet, Main (Mikuni 152.5) (3G2-14231-
3G2-14231-81-A0
152.5 is the OEM Mikuni jet size
https://www.ronayers.com/oemparts/a/yam/50042e28f8700209bc78a2ba/carburetor
Here is a Dynojet to Mikuni chart (thanks to CaptainKyle ([email protected]), a good source of parts and work, as are other members on here:
https://yamaha-enduros.com/index.php/workshop/carb-jet-conversion-chart
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Thanks for the quick reply. Im in Fort Lauderdale. There is a hose running from the oil cap up towards the area around the carbs but it vents to the air. Two of the pods have vent ports on the tops but no hoses are connected.
Now that you mention it the holes in both 170 jets do appear slightly different. One appears to be bigger than the other.
I only see two rubber plugs in the jet block and one is in bad shape. Does this look right?
Now that you mention it the holes in both 170 jets do appear slightly different. One appears to be bigger than the other.
I only see two rubber plugs in the jet block and one is in bad shape. Does this look right?
I PM'ed you.
You're on the right track as-far as you've gotten.
Yes to the rubber plugs being there. 'Bad' as to their condition! You should order four new plugs of each size, a total of eight for all your four jet blocks.
Part #43 in the carburetor fiche below
Cap (for pilot jet, four caps are required; these are the left-side, smaller ones)
22V-14968-00-00
$6.52 each
Part #45 in the carburetor fiche below
Cap (for main bleed pipe, four caps are required; these are for the middle hole, which is larger-diameter)
22U-14968-00-00
$6.18 each
Note that there is no rubber plug/cap for the right jet block hole. It is a metal-plugged circuit. You can see the brass plug. Do not disturb it.
I suggest you consider buying four new pilot jets, they aren't expensive, and because of their small diameter, they are easily-damaged when you try to remove them. The narrow diameter often causes one which is either corroded in-place, or over-torqued upon installation to strip-out the slotted screwdriver slot on the head of the jet. When you get that sickening feeling of the slot crumbling without the jet coming-unscrewed, well, now you're screwed! Literally. I recently-posted about how to do this type of broken pilot-jet removal. Look under my name in the 'how-to' section.
Here it is:
https://www.vmaxforum.net/threads/h...lot-jet-with-a-broken-screwdriver-slot.49066/
Part #42 in the carburetor fiche, below
Jet, Pilot (#37.5)
4G0-14142-37-A0
$6.10 each
In my experience, the pilot jets easily become plugged, leading to poor operation at or just-above idle. This can manifest itself in a non-sparking cylinder at idle, as the engine doesn't have the proper fuel/air mixture to fire. You end-up with a poor, uneven idle and a 'cold' exhaust header, because they cylinder isn't firing at-idle. Get higher up in the rev range where the pilot jet doesn't control the air/fuel mix, and now the 'dead' cylinder begins to-fire, normally. A rusty gas tank is often the cause of the plugged pilot jet. Clean your carbs but neglect to clean your gas tank and change the fuel filter, and you're just gonna face another carburetor removal and cleaning.
There is supposed to be a collector canister which allows the oil vapor to drain back into the engine through that big rubber hose to the oil cap. Evidently you are missing the collector canister. Oil mist from the crankcase is directed into the canister, and the oil falls-out of suspension in the oil/air mix, in the canister, and drains through that big hose into the engine cases. The canister is usually filled (loosely-packed) with something like stainless-steel woven material, looking like a brillo pad. That material allows the oil to run-down it to the bottom of the canister to the hose, to the oil filler cap. Don't your air pod filters have spigots on the top? OK, I see you say they do.
Left open to the atmosphere, you could have your engine become oil-soaked if you run it hard. Crankcase pressure will vent unrestricted out the hose. If you look on here, in the factory instructions, you can find the Dynojet Stage 7 directions which have installation instructions you can follow. You can make your own oil drain from some PVC fittings, or buy a new one or a used one, try Sean Morley, you already know him. [email protected]
The DJ Stage 7 instructions have you place a restrictor in the stock OEM crankcase vent tube (see #7 in the DL Stage 7 instructions, link, below).
OK, I think I know what you're looking at, the pilot air jet under the CV carb diaphragm is a 170. Coincidentally, your Dynojet main jet is a 170, different things.
I saved you some time:
https://www.dynojet.com/amfile/file/download/file/dba4312ca3d2e4300bbc585338c473be/product/3785/
Do you still have VBoost, or has it been removed? Below the carbs, is there a butterfly pair, or do you have just aluminum tubes running from the front cylinders to the rear cylinders? It will be easier to synch your carbs with a set of bourdon tube gauges if the VBoost is still in-place; the Dynojet Stage 7 tells you to remove the VBoost and to install tubes in-pace of the butterflies. You don't need to do that. I run Stage 7 jets and I kept my VBoost.
Here's a comparison of CV slides' needles, which is yours?
From left to right:
Dynojet Stage 1 (if you have these, throw them away or use them for martini olive spears, they are problematic
Dynojet Stage 7 These are good if you know how to tune to them
Factory Pro These are good with the Factory Pro kit
OEM USA models VMax Mikuni needles, you may-notice there is only one groove, while the others have multiple grooves, aiding tuning them; supposedly the Canadian VMax models also came with multiple grooves on the stock Mikuni needles. Shimming a stock Mikuni one-groove needle with thin washers is another way of changing the fuel-air mix during the RPM range that the needle controls the fuel/air mix.
You're on the right track as-far as you've gotten.
Yes to the rubber plugs being there. 'Bad' as to their condition! You should order four new plugs of each size, a total of eight for all your four jet blocks.
Part #43 in the carburetor fiche below
Cap (for pilot jet, four caps are required; these are the left-side, smaller ones)
22V-14968-00-00
$6.52 each
Part #45 in the carburetor fiche below
Cap (for main bleed pipe, four caps are required; these are for the middle hole, which is larger-diameter)
22U-14968-00-00
$6.18 each
Note that there is no rubber plug/cap for the right jet block hole. It is a metal-plugged circuit. You can see the brass plug. Do not disturb it.
I suggest you consider buying four new pilot jets, they aren't expensive, and because of their small diameter, they are easily-damaged when you try to remove them. The narrow diameter often causes one which is either corroded in-place, or over-torqued upon installation to strip-out the slotted screwdriver slot on the head of the jet. When you get that sickening feeling of the slot crumbling without the jet coming-unscrewed, well, now you're screwed! Literally. I recently-posted about how to do this type of broken pilot-jet removal. Look under my name in the 'how-to' section.
Here it is:
https://www.vmaxforum.net/threads/h...lot-jet-with-a-broken-screwdriver-slot.49066/
Part #42 in the carburetor fiche, below
Jet, Pilot (#37.5)
4G0-14142-37-A0
$6.10 each
In my experience, the pilot jets easily become plugged, leading to poor operation at or just-above idle. This can manifest itself in a non-sparking cylinder at idle, as the engine doesn't have the proper fuel/air mixture to fire. You end-up with a poor, uneven idle and a 'cold' exhaust header, because they cylinder isn't firing at-idle. Get higher up in the rev range where the pilot jet doesn't control the air/fuel mix, and now the 'dead' cylinder begins to-fire, normally. A rusty gas tank is often the cause of the plugged pilot jet. Clean your carbs but neglect to clean your gas tank and change the fuel filter, and you're just gonna face another carburetor removal and cleaning.
There is supposed to be a collector canister which allows the oil vapor to drain back into the engine through that big rubber hose to the oil cap. Evidently you are missing the collector canister. Oil mist from the crankcase is directed into the canister, and the oil falls-out of suspension in the oil/air mix, in the canister, and drains through that big hose into the engine cases. The canister is usually filled (loosely-packed) with something like stainless-steel woven material, looking like a brillo pad. That material allows the oil to run-down it to the bottom of the canister to the hose, to the oil filler cap. Don't your air pod filters have spigots on the top? OK, I see you say they do.
Left open to the atmosphere, you could have your engine become oil-soaked if you run it hard. Crankcase pressure will vent unrestricted out the hose. If you look on here, in the factory instructions, you can find the Dynojet Stage 7 directions which have installation instructions you can follow. You can make your own oil drain from some PVC fittings, or buy a new one or a used one, try Sean Morley, you already know him. [email protected]
The DJ Stage 7 instructions have you place a restrictor in the stock OEM crankcase vent tube (see #7 in the DL Stage 7 instructions, link, below).
OK, I think I know what you're looking at, the pilot air jet under the CV carb diaphragm is a 170. Coincidentally, your Dynojet main jet is a 170, different things.
I saved you some time:
https://www.dynojet.com/amfile/file/download/file/dba4312ca3d2e4300bbc585338c473be/product/3785/
Do you still have VBoost, or has it been removed? Below the carbs, is there a butterfly pair, or do you have just aluminum tubes running from the front cylinders to the rear cylinders? It will be easier to synch your carbs with a set of bourdon tube gauges if the VBoost is still in-place; the Dynojet Stage 7 tells you to remove the VBoost and to install tubes in-pace of the butterflies. You don't need to do that. I run Stage 7 jets and I kept my VBoost.
Here's a comparison of CV slides' needles, which is yours?
From left to right:
Dynojet Stage 1 (if you have these, throw them away or use them for martini olive spears, they are problematic
Dynojet Stage 7 These are good if you know how to tune to them
Factory Pro These are good with the Factory Pro kit
OEM USA models VMax Mikuni needles, you may-notice there is only one groove, while the others have multiple grooves, aiding tuning them; supposedly the Canadian VMax models also came with multiple grooves on the stock Mikuni needles. Shimming a stock Mikuni one-groove needle with thin washers is another way of changing the fuel-air mix during the RPM range that the needle controls the fuel/air mix.
Last edited:
Yes. The front two pods have spigots on top but no hoses. After you told me about the stage 7 I just went online looking for the instructions. I have experience with inline 4's. I have two 70's CB750s which I built but this is my first vmax. The hard part now is trying to figure out what has been done to the bike by previous owners. I believe the Vboost is still in place. I know the servo and cable are hooked to something. I will look again when I get home. So far everything else looks ok. I noticed that besides the one on the carbs, none of the bolts on the motor or chassis show signs of being messed with. I checked the valve clearance and only the intake valves on cylinder 3 were a little tight. ( .076mm would fit but .102 mm would not). Sean has me on the list for the shim kit as well. This my needle. It looks like the first one to me.
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OMG!!!!
What the "Pre-cognition" woman told Tom Cruise in "Minority Report," a fine science-fiction story by Philip K Dick:
"RUUNNNN!"
Those Dynojet Stage 1 needles are the Devils' Spawn! Read on-here about all the problems that people have trying to make those work. The guys like CaptainKyle, Sean Morley, and dannymax who are professional mechanics or specialists in our induction systems will tell you, "stay-away from the Dynojet Stage 1 jet kit components!" Even going back-to the OEM 1-groove needles will run better than DJ Stage 1 needles.
Sean Morley offers a Morley's Muscle jet kit and air cleaner/OEM airbox lid modded. Since you already have the 4 air pods, you might consider doing the Stage 7 needles, leaving-alone your VBoost, and going leaner on your main jets, to a 147.5 or a 150. I have a 4/1, Stage 7 needles and a K&N 4 pod set, using 147.5 jets, and I kept the VBoost, I like how it runs. Sean can sell you individual K&N components, he's a dealer. I suspect that you are running 'way-too-rich.
What the "Pre-cognition" woman told Tom Cruise in "Minority Report," a fine science-fiction story by Philip K Dick:
"RUUNNNN!"
Those Dynojet Stage 1 needles are the Devils' Spawn! Read on-here about all the problems that people have trying to make those work. The guys like CaptainKyle, Sean Morley, and dannymax who are professional mechanics or specialists in our induction systems will tell you, "stay-away from the Dynojet Stage 1 jet kit components!" Even going back-to the OEM 1-groove needles will run better than DJ Stage 1 needles.
Sean Morley offers a Morley's Muscle jet kit and air cleaner/OEM airbox lid modded. Since you already have the 4 air pods, you might consider doing the Stage 7 needles, leaving-alone your VBoost, and going leaner on your main jets, to a 147.5 or a 150. I have a 4/1, Stage 7 needles and a K&N 4 pod set, using 147.5 jets, and I kept the VBoost, I like how it runs. Sean can sell you individual K&N components, he's a dealer. I suspect that you are running 'way-too-rich.
Ohhhh Fuuuuudddddggggeee!!. This is what I hate about previous owners. So I just checked and my Vboost is still installed. I just opened the tops on the other carbs and they all have the same needles as this. I am going to take your advice and grab a set of Stage 7 needles since I'm mostly there already. Any idea where I can buy them ?
Sean Morley-Morley's Muscle, check his facebook presence. [email protected]
When you turn -on the key, can you see/hear the VBoost cycle open, then closed? Since the carbs are off that should be a cinch. Buy the Mikuni 147.5 and/or 150 main jets. Your bike is likely going to be a whole 'nother animal when you're done, I strongly-urge you to NOT USE the Dynojet 170 main jets!
Have a dialogue with Sean about the air correctors in the Dynojet kit, the drilling of the slides (what size drill to use on the hole closest-to the outer edge of the slide; easily-reversed with a bit of epoxy should you decide to go back to entirely-stock; DO NOT DRILL the slide needle hole!) and the cheap-man's modification for the slide springs, using some safety wire to tie-up a few coils of the springs to effectively shorten them. Sean may be able to give you a length to end-up at for that.
Assuming that your bike is OK otherwise, you will be surprised to see the performance of VBoost. What you bought, the way it ran, is going to be a big change to how it will run, now.
Yes you can hear it cycle and all the components appear to be attached. I just took a closer look at the parts from this carb and the slide have been drilled, (I matched them with a #19 drill bit, same as mentioned in the Dynojet instruction). I will get the jets you mentioned and I am very grateful for your help.
When it's back together and you've ridden it a few times, tell us about it.
