1999 YZ 400f Carb issues

I have a gas dripping (sometimes pouring) from the very bottom over flow line of the carb.....any ideas?????


Your carburettor is overflowing because the float valve is not shutting off.

This can be caused by dirt under the valve, a worn valve, or incorrect float height.

How long has the problem been happening. If it just started, give the float bowl a tap with the head of a screw driver, sometimes this helps dislodge some dirt under the valve and fixes the problem. If this doesn't work, you will have to strip the carburettor.

Also see other posts of today's date on this subject for a 400F.

just got this 99 yz400f bike on a trade and the header on it got red hot....wow whats going on there?

The YZ400 does not like being left at idle for too long, it prefers to be moving. Also the header pipe is very thin so extended period of idle will cause the header to glow. This is a common observation. If you search the forum you will find you are bot the first to have shown concern at a red hot header.

thanks for the reply...yamaha said i was running way too lean and that it could seize the bike up.....it glows red almost as soon as it warms up...im going to melt my leg off and then light a smoke off the header:banghead:

ok so i got the bike out in the open and no red glow...runs like a raped ape...and idles fine....one more concern though,,the over flow tube that hangs down at the bottom of the motor drips alittle oil...ok im fine with that its there for a reason, but the oil looks alittle milky...but then again the motor was just rebuilt....do i have a need to be concerned...is it a blown head gaskett?? or should i take it out for a couple rides and see if it clears up?

It will drip oil, it may also look milky. My old yz426 would coat my boot in milky looking oil with both motors I had (stock and 444).

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