Carb problem

[oldyam80sg]

So, after cleaning the carbs better than I ever did and removing the Pingel vacuum valve from the equation, I hooked up my Motion Pro auxiliary gas tank to test to make sure no leaks. Everything was fine until the carb closest to the throttle started to have fuel come out the air filter side. Because there is no airbox, I removed my air filter setup and could see fuel coming out of the boot when the bike was running. I ran the bike unitil it shut off due to lack of fuel. I removed the carbs and removed the float bowl on the carb. Everything looked Ok, I replaced the float needle with a brand new one and took off the carb bowl next to it as it looked like something had dried on the side of it. There were actually 2 gaskets on the carb, so I removed both and replaced it with a brand-new gasket-genuine Yamaha. Reinstalled both float bowls and put the carbs back on the bike. Now the 2nd carb from the throttle side, as soon as I turned on the fuel tap, fuel poured of the carb without it running. Why? Did running the carbs until they ran out of fuel cause the float to hang up?

[bikerphil]

Ok, if you're using an auxiliary tank, it is probably hanging much higher than the normal bike fuel tank creating too much fuel pressure.

[oldyam80sg]

Interesting Phil-I would have never thought that. So, if I lower aux tank maybe that will help? It's on a 6 Foot ladder up on top rung.

[oldyam80sg]

Phil-why would these 2 specific carbs have issues? When I turn on the fuel, gas comes out of 2nd carb inward without it running what would cause this? Flooding?

[bikerphil]

Stuck float probably, when initially filling the bowls, tap the bowls with a screwdriver handle, see if that stops the leak.

Yes lower the tank to normal fuel tank height.

[oldyam80sg]

Ok many thanks Phil-when it was running no choke it was idling around 900 rpm. and sounded really good. Will try again tomorrow.

[motoman]

Having a float hang up not properly allowing float needle to seat properly is more than likely float bowl gasket is protruding a tad beyond beyond bowl on inside. I suggest removing all four float bowls and with gasket in place use a razor blade and and slice off any of gasket using inner portion of bowl as a guide. Also check that each float is paralel with inner portion of bowls as clearance is minimal at best.

[Bonz]

Having a float hang up not properly allowing float needle to seat properly is more than likely float bowl gasket is protruding a tad beyond beyond bowl on inside. I suggest removing all four float bowls and with gasket in place use a razor blade and and slice off any of gasket using inner portion of bowl as a guide. Also check that each float is paralel with inner portion of bowls as clearance is minimal at best.

^^^This^^^

I've hung my auxiliary fuel source three feet higher from a clothes hanger in the garage than what the normal tank would be on many bikes and that has never been an issue.

Did some reading and water pressure, which could be equated to fuel pressure, increases .433 PSI per vertical foot of elevation. Going from 3 ft off the ground to 6 ft off the ground is a difference of about 1.3 PSI in the pressure of the fuel. I don't think that's enough to make a difference in a properly functioning set of carburetors. Meaning if there is nothing otherwise
impeding the float from doing its job and closing off the fuel flow.

[oldyam80sg]

I took an X acto knife and trimmed a sliver of gasket and checked to make sure float was not hanging up. I tapped on the bowls with a screwdriver handle and started the bike with the aux tank not really high. There was a slight drop in the line. The bike started and now no leaks. Will try it again tomorrow.

[motoman]

I took an X acto knife and trimmed a sliver of gasket and checked to make sure float was not hanging up. I tapped on the bowls with a screwdriver handle and started the bike with the aux tank not really high. There was a slight drop in the line. The bike started and now no leaks. Will try it again tomorrow.

Very likely, the carb gasket trim solved the float hanging up issue overflowing the carb with fuel.

[DiverRay]

If you have a problem on the next test, check the metal floats for leaks! A pinhole WILL cause the float to fill with gas, and then drop lower than it should, causing flooding. I've had that problem more than one time!

[oldyam80sg]

The bike does not leak and purrs like a kitten. Time to start putting on my new Pingel vacuum valve and new fuel line.

[cajun31]

If you have a problem on the next test, check the metal floats for leaks! A pinhole WILL cause the float to fill with gas, and then drop lower than it should, causing flooding. I've had that problem more than one time!

I am guessing you have personal knowledge on his carbs? I didn't think his carbs had metal floats unless changed to them. My experience has always been that the year bike he has came with carbs with the solid black floats. The only reason I ask is to not confuse others reading this message string. I have read both the OPMs threads concerning his carb problems and no where do I see where he states the carbs on his bike are from and earlier model bike.

[oldyam80sg]

The carbs have the solid black floats and I have the float needles with the rubber tips (Viton?) Need to replace the fuel filters as I broke one today.

[cajun31]

The carbs have the solid black floats and I have the float needles with the rubber tips (Viton?) Need to replace the fuel filters as I broke one today.

Those internal fuel filters are still available through Partzilla.