puking gas even while riding

6 replies to this topic
  • r6speed

Posted July 29, 2010 - 05:18 PM


99 YZ400F Keihin Carb
a while back I had a problem with the pilot getting clogged up, got it all cleaned out and back to normal:banana:

Before any of that ever happened the bike always puked gas when I would leave the gas on after riding:banghead:

But now (just started) its puking gas even while I'm riding:foul:

The only way to get the gas to stop is turn off the petcock so what would cause this and what should I do? Thanks in advance

  • grayracer513

Posted July 29, 2010 - 06:25 PM


Check and replace the float needle and seat assembly as necessary.

  • laserracer

Posted July 29, 2010 - 06:33 PM


if the float needle and seat look ok ...theres a little o ring i think it goes around the seat ...mine looked more like a flattened plastic ring ..than a rubber O ring
i replaced the O ring and no more leaky problems ..:smirk:

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  • r6speed

Posted July 30, 2010 - 05:41 PM


Thanks for the info! Pulled the carb today and noticed while I had it off that when the throttle was flipped the accel pump rod was squirting a bit of gas, looked like the little rubber cover was kind of pinched so made sure it went back on right.
Turned out to be that little rubber o ring/washer, put the new one and put it all back together and boom no leaky...BUT NOW I GOT BIGGER PROBLEMS

Even after cleaning with 3 cans of carb cleaner and about a half hour of air hose I still managed to get something in my pilot jet I guess cause now its cutting out when throttle is snapped open really quick ( I have had this problem before and had to clean out the pilot jet). But not only do I have that problem now but my accel pump rod is squirting gas everywhere! It didn't seem to do it the first few minutes of riding but shortly started and its not pinched!?!?!? I don't know what to do I'm aggrivated

EDIT: cooled off a bit and went back out. Its squirting right out of the bottom (acelerator side) of the rubber boot, but the boot looks fine. Its doing it anytime I twist the throttle weather the gas is on or off...what would cause there to be extra pressure there? Or is it simply I need a new boot?

Edited by r6speed, July 30, 2010 - 06:07 PM.

  • grayracer513

Posted July 30, 2010 - 08:33 PM


The boot is not intended to seal fluid in, it's supposed to keep dirt out. In fact, there's not supposed to be any fluid under it. Your accelerator pump diaphragm is ruptured. Back to the parts store.

  • r6speed

Posted July 30, 2010 - 11:08 PM


yep back I go, but at least I know what I'm getting.
Thank you!

  • r6speed

Posted July 31, 2010 - 09:36 PM


Got it all cleaned back out and back together today with the new diaphragm and runs 100% :banana:

Thanks to both of you for the help its greatly appriciated!

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