removed fuel pump,installed new float valve,removed carb inlet screen and bike ran great!next day tried to start it up and it died and would not turn over.then it started leaking gas.pulled the plugs and they were fouled.cleaned plugs and tried to startup but same results.Friends say float valve is sticking.I followed instructions very carefuly doing this mod.before I take apart the carb again is there anything else I can do to fix this issue?Thanks in advance.

JYD wrote:
removed fuel pump,installed new float valve,removed carb inlet screen and bike ran great!next day tried to start it up and it died and would not turn over.then it started leaking gas.pulled the plugs and they were fouled.cleaned plugs and tried to startup but same results.Friends say float valve is sticking.I followed instructions very carefuly doing this mod.before I take apart the carb again is there anything else I can do to fix this issue?Thanks in advance.

Just an FYI, when we had that problem back in my racing days as well as with outboard motors, we used to pull the plugs and coil wire and crank the motor for a while without the plugs in so we could dry the fuel out of the cylinders. Just cleaning the plugs isn't enough because there's usually still fuel inside the cylinder chambers.

Then after fixing the fuel problem, such as improperly set float levels, we'd put it back together and crank it back up. You pull the coil to avoid accidentally lighting up the fuel that's blowing out of the cylinders through the spark plug holes.

Your problem could be as simple as the float level set too high, not allowing the fuel to shut off, so the fuel's constantly running. When you first put it together and cranked it up the motor was simply burning the excess fuel flow. But when you shut it off and let it sit the fuel flooded your engine (and probably into your crank oil as well) so it wouldn't fire at all. If everything had completely dried out again it probably would have ran the way it did the first time, until it sat and leaked back into the cylinders.

It's also possible that when you put it back together the float or float needle was slightly ajar and sticking, not allowing it to work properly.

The key is that you said it was running great until it sat. The most practical reason that the fuel kept flowing was because something was stuck or the float level is too high. If you somehow got the wrong float needle (can't recall if that's the correct name for it) it may not be seating into the jet properly or there may even be some crud caught in the jet that's not allowing the needle to sit all the way in. Crud may be your culprit.

Dry it all out, pull the carb apart, check for crud in the float jet and your float level, and try again. It's most likely the level or a piece of crud below the needle, unless you have the wrong needle altogether...

Oh and another thought. Are you shutting off your fuel at the petcock after you shut your motor down, or even a little before? If you are but the fuel's still running then you need to pick up a petcock gasket kit and rebuild it. Mine was leaking when I bought my bike and rebuilding it was a real plus.

If your bike was running fine you should be able to shut the fuel off before stopping the motor and it should run fine again when you turn the fuel back on and start it back up because the bike will burn the excess fuel leakage.

I'm guessing crud beneath the float needle which isn't allowing it to seal up.

JYD wrote:
removed fuel pump,installed new float valve,removed carb inlet screen and bike ran great!next day tried to start it up and it died and would not turn over.then it started leaking gas.pulled the plugs and they were fouled.cleaned plugs and tried to startup but same results.Friends say float valve is sticking.I followed instructions very carefuly doing this mod.before I take apart the carb again is there anything else I can do to fix this issue?Thanks in advance.


It happens from time to time, that a small piece of something will get stuck in the seat area and prevent the needle from seating correctly. I had the same thing happen to me when I went pumpless on one of mine. Like you, it was the very next day, after it ran just fine the day before.

Shut the fuel off at the petcock. Open the bowl drain, after slipping a tube on it. Drain the bowl, and while the bowl drain is open, open the petcock and let the fuel flush out whatever is holding things open.
Button things back up. Put the bike in gear and rock it back and forth a bit in case there is fuel in a cylinder. This should help loosen things up, so the starter can spin the motor.
Open the throttle wide open, and hold it there and hit the start button. Don't have anything you value behind the bike, because it'll spit gas and carbon and crud all over the place when it catches.

If this doesn't work, then you'll have to pull the carb and find out what's wrong.

I always turn my fuel off about 30 or 40 secs before turning the key off when I stop. Especially when I know the bike won't be attended for awhile.

SKWEARpeg wrote:


It happens from time to time, that a small piece of something will get stuck in the seat area and prevent the needle from seating correctly. I had the same thing happen to me when I went pumpless on one of mine. Like you, it was the very next day, after it ran just fine the day before.

Shut the fuel off at the petcock. Open the bowl drain, after slipping a tube on it. Drain the bowl, and while the bowl drain is open, open the petcock and let the fuel flush out whatever is holding things open.
Button things back up. Put the bike in gear and rock it back and forth a bit in case there is fuel in a cylinder. This should help loosen things up, so the starter can spin the motor.

Open the throttle wide open, and hold it there and hit the start button. Don't have anything you value behind the bike, because it'll spit gas and carbon and crud all over the place when it catches.


Great idea and advice.

Perhaps better yet to pull the fuel line from the petcock and blow through it to create more pressure to shove the crud out of the jet and up past the float needle? And beyond that out of the bowl drain to be sure it's been expelled?

Any concerns with fuel in the crank after you had your issue, SKWEARpeg?

Blowing is not really necessary. As long as the float is holding pressure on the needle, it pinches against whatever may be stuck and holds it Drain the bowl, and open the petcock and the fuel can wash it out.
The fuel should cook off when the engine temps start climbing. A one time deal like this is not as serious as a continuous leak of this sort. It's kind of up to the bikes owner. I didn't, but It'd never hurts to error on the side of caution.

A friend has told me there may be dirt causing the valve to stick open.he suggested spraying carb cleaner into the carb to free the dirt.dont know if that will do the trick.BTW float valve used is Yam part#5KM-14190-30-00 taken from tech article on this site.gas leaking from hose normally attached to the back of stock air filter.I have the V102 flamed filter without an attachment for this hose.Also is it necessary to have to shut off the fuel when stopped after doing this mod?Thanks

JYD wrote:
A friend has told me there may be dirt causing the valve to stick open.he suggested spraying carb cleaner into the carb to free the dirt.dont know if that will do the trick.BTW float valve used is Yam part#5KM-14190-30-00 taken from tech article on this site.gas leaking from hose normally attached to the back of stock air filter.I have the V102 flamed filter without an attachment for this hose.Also is it necessary to have to shut off the fuel when stopped after doing this mod?Thanks


If you read the bikes owners manual, you will see that yamaha recommends shutting the fuel off at the petcock, anytime you're going to leave the bike unattended. That is with the pump. I do it before turninng the bike off with the key, so the fuel level in the bowl is reduced enough, the needle no longer makes contact with the seat. This helps avoid those instances where stuff dries and leaves a film or crud in the seat area, and prevents a good seal there.
The fuel is coming out of the bowl vent. That's typical, when a float valve is leaking, or is stuck open. Since yours worked fine and now it doesn't, then I would suspect some small piece of crud or something was either knocked loose when you were working on the carb, or was inside the fuel line, and found its way to the needle and seat area. It doesn't have to be very big.

If you are going to blast carb cleaner into the carb, the place to do it, would be where the fuel line attaches to the carb. In this instance, if you don't do it there, then you might as well blast it into your hip pocket. The affect would be the same. Follow the directions I gave you in the post earlier in this thread. If it still has a problem then pull the carb, and find out what is preventing the needle and seat from working properly.

I would buy a long enough piece of hose to extend the line from the carb vent, down to a location below the bike. Then when it spits fuel in rare instances like this, it dumps on the ground. You would be surprised how common it is for people with pumps to experience this from heat, or when the bike has been stored and the fuel in the bowl has dried in a manner so the float valve sticks open. When the pump starts pushing fuel out of the carb vent, it's really exciting.