Probably the lowest MPG you'll ever see!

[Omran]

Hey guys, let me just explain first that where I am there is not a lot of good mechanics for me to just go and drop off my bike and explain my problem and pass by a few days later to pick my fixed bike up.

Where I am, I go through one hell of a hassle just to find replacement levers for my bike. Anyway, to cut the story short, I own a 1992 VMax, the V-Boost version!

I bought this bike used, and I noticed something from the first week, on a full fuel tank, the bike runs about 60 KM, then the sexy fuel light comes on at which point I open the reserve switch giving me 30 more kilometers to go :clapping:

Now this can be very annoying when I want to travel or even go for *average* rides with my bike. I took it to a mechanic who took the carbs out and took them apart, gave them a good clean, adjusted the needles and screws and replaced all 4 spark plugs with 4 new NGK R ones, the bike came out sounding perfect, I used it for 2 days, it started misfiring and lagging, took the sparkplugs out to check them and found the rear 2 all covered in black, and the front two looking relatively cleaner.

Now I'm guessing there's something wrong with the setting of the carbs or with the needles or something, but the exhaust smells like raw fuel.

I've gone head over heals trying to find a fix for this with no luck, so can you please shed some light on what might be ruining my spark plugs and limiting me to the 90 KM ride?

 

[Diablotin]

The raw smell can come from bad float level. You should check them and move from there.
How many turns do you have on the A/F screws?

Sent from my GT-I9100 using Tapatalk 2

 

[davesax36]

Post the following info:
A/F screw turns in until seated --
Spark plug gap --
Wet float level --
Pics of plugs.

We'll get you through it. I had a similar issue. Low fuel light came on at 50 miles... It sucked, but was a fairly simple fix.

 

[Rusty McNeil]

Might also be a previous owner thing?
Someone was in the carbs and messed them up perhaps?

Its very easy to put the wrong jets in the wrong place.

If you look in the top of the carbs the paj1 jets should be 90 or 100

Pull the slide diaphragm covers, springs and slides and the jets behind there, paj2, are usually 170's

Can't check the mains without pulling the carbs.

Might also do a float level "wet" check

You say he Adjusted the needles? Does it have after market jet kit. Factory needles usually aren't adjustable.

Normal a/f screw adjustment is somewhere around 2 1/3 to 3 1/2 turn out.

Close perhaps stuck partially open. They are the little plungers that have a little claw that pulls them out when you move the choke lever.

They aren't really chokes, they are fuel enrichment circuits so might could cause this.

The carbs/fuel section on here will have a lot of stickies that can guide you through checking some of these things as well.

All the jet sizes I mentioned are stock
Mikuni numbers. If they are DynoJet they can be different and the two don't compare numerically. There is a cross reference to help with that out there somewhere.

 

[pjmac5]

Now this can be very annoying when I want to travel or even go for *average* rides with my bike. I took it to a mechanic who took the carbs out and took them apart, gave them a good clean, adjusted the needles and screws and replaced all 4 spark plugs with 4 new NGK R ones, the bike came out sounding perfect, I used it for 2 days, it started misfiring and lagging, took the sparkplugs out to check them and found the rear 2 all covered in black, and the front two looking relatively cleaner.

I went through something like this. Previous owner of my VMAX screwed up the carbs by changing jets and needles and never got it right. I hauled the bike to a mechanic who wanted $600 to rebuild the carbs. I took the bike home and used the vast information on this forum to fix the bike myself.

First, call the mechanic and find out Main Jet size and brand as well as Needle information. Are the Needles stock or aftermarket. If aftermarket, what grooves are the clips on. If everything is within reason (ask the forum) then it might be as simple as getting the A/F mixture correct.

Next, clean the plugs and reinstall them. If you turn the screws in, you are making the mixture leaner. If you turn the screw out, you are making the mixture richer. Clearly, you want leaner.

Adjust each Carb one at a time. Screw the A/F screw all the way in until it seats. Count the number of turns and fractional turns required until the screw seats (be gentle and exact, yes a 1/4 turn matters). Back the screw out. For the back carbs, subtract 1/2 a turn. For the front subtract 1/4 turn. So now you know where you are at on each Carb and you should be leaner if A/F screws are functional. Ride the shit out of the bike for 15-20 minutes (don't just pudder around the block), then let it cool down and pull the plugs again. From here make very small adjustments 1/8-1/4 turn in or out depending on how the plugs look. Repeat this a few times until you the plugs look good.

If the Mechanic installed or kept in Jets that are too large, then you need to change them before you do anything else. If he doesn't know this information, then I would wonder if he did any of the work at all.

 

[06VMAXIMUS]

If it ran great for 2 days then went to crap, I would think you might have some rust in your fuel tank that has made its way back into the carbs. I would suggest taking a look in your tank with a light and see if its rusty. Was the fuel filter changed when the mechanic cleaned the carbs? If crap gets into the bowls, it can cause the fuel needles to jam and overflow......which can drown the cyls with fuel.

 

[[email protected]]

You need to learn to work on this bike for yourself. The resources are here. If you have some basic hand tools, and aren't afraid to get your hands dirty, doing some research, and learning, you can do it.

Keep it simple. Air, fuel, and spark are what is needed to make an engine run.

Install new plugs. Stock ones. Do a spark test. If you have good spark move down the list.

There are step by step instructions on this forum for removing the carbs, rebuilding the carbs, setting float height, checking float height, and synching the carbs. I would find these threads, print them out, and get to work.

Check the tank for rust. If any signs of rust, clean the tank, replace the fuel filter, and clean out the fuel lines.

If you need any parts, you can work with Morleys Muscle. Sean ships all across the globe, has many parts in stock, prices are fair, probably the most knowlegable vmax vendor on the planet. [email protected]

 

[Traumahawk]

If you have issues, with working on the Vmax...I would suggest Damon Ferraiuolo's videos.

Here's the thread where I talk about getting them.

http://vmaxforum.net/showthread.php?t=28760&highlight=damon

 

[Fire-medic]

My long-time friend & Yamaha factory mechanic, Bill Boyce of Riva Yamaha, Pompano Beach FL, gave me some great advice. He has been a Yamaha mechanic since before the VMax was released, and has done many mods to them. I was getting my VMax back on the road after a long period of inactivity. He told me, "look-inside the gas tank and if you see significant rust, replace the tank w/a new one. The time you spend trying to make your old tank work, and having to clean your carbs repeatedly as rust clogs them, just isn't worth messing-with." I bought a new tank for Ron Ayres Yamaha, and once the carbs were done, no-further issues.

You have lots of good advice in the thread. You can do the work if you have someplace to work, and a few common tools. Damon's videos are supposed to be user-friendly, I don't have a set, but they are very inexpensive, and you can refer to them repeatedly as you go through the process of re-doing your carbs, if you have-to.

A suggestion: straight-jaw ViseGrips 10" are very useful for loosening float bowl and CV diaphragm caps. Be very careful if you decide to use an impact driver to try & loosen screws as the carbs are made of potmetal and will crack readily! :confused2: You are better-off using the ViseGrips and a new screwdriver , maybe w/some rubbing compound on the X to give the screwdriver tip a better grip.

If you absolutely insist on re-using your tank, and you want to seal it, I think the best choice from what I have read of from comments on here is probably POR-15,
http://search.eastwood.com/ppc/por+...=31015452300&gclid=CLKWqLOIsroCFUdk7AodI3MAng
but you have to follow the directions exactly! One of the readers didn't and ended up w/continuing problems. I have used POR-15 for other rust issues not in a gas tank, and the stuff works-great.

 

[TheTwistedNomad]

I don't know where Heliopolis is but you should see if other Vmax owners are around your area from the forum and can help you if you need it. The info fellow forum members post are invaluable but sometimes you need someone to show you the ropes instead of reading instructions and looking at pictures. The more you get your hands dirty the more you love the bike I think.