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miketegra

yz426 leaking gas after carb clean

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I put in a new idle jet and cleaned the carb on my 2000 yz426. Put it all back together and now it leaks gas as soon as I turn the gas on.

Float is not sticking and float level appears to be correct.

I took the bowl off and hooked up the gas to the carb then pushed the float up to the position it would be in if it was floating in gas with the bowl on, then turned on the gas, and gas was still coming out of the needle valve/seat area.

The o-ring on the seat looked pretty flattened out...not cracked, but appeared to be almost flush with the rest of the seat. I noticed the seat almost felt loose when I put it in the carb body (without the retaining screw attached).

Am I correct in assuming its either the needle valve or the valve seat o-ring that is the problem?

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Am I correct in assuming its either the needle valve or the valve seat o-ring that is the problem?

Fairly obviously. The tip of the needle may be dried out or cracked, as might the O-ring sealing the seat to the carb body.

Interestingly, Honda actually sells individual O-rings for several things that Yamaha doesn't, and I believe the needle seat ring is either available separately, or as a part of a kit that costs considerably less than a needle & seat.

Another possibility, believe it or not, is that the dried out parts may recover after they are re-wet in fuel for a couple days. The problem may also be a piece of dirt that will rinse away.

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Thanks for the info. The tip of the needle looks pretty good actually...no cracks and it doesn't look worn. I suspect the seat o-ring is the culprit. I checked the fiche and it appears that they only sell the needle and seat as a set. Do you have more info on the "kit" you mentioned?

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