Carb overflow problem??

7 replies to this topic
  • Michael Cahill

Posted March 07, 2008 - 06:23 PM


I have a 98 YZ400f, and just recently the carb started leaking out of the overflow tube when the bike was sitting. (just a tiny drip tho, a little puddle on the floor in the morning)

ive already took the float valve out and reset it to the manual spec's, and gave it a through cleaning, but it is still slightly leaking.

so what im asking is, should i replace the float valve? (or is there something simple i can do to fix it?)

Or should i just get a new fuel cock on the gas tank, and stop the gas flow that way? (because it has never shut off right)
Because the bike runs great the way it is now.

Thanks, Michael

  • grayracer513

Posted March 07, 2008 - 06:57 PM


You'll probably need to do both, to tell the truth.

  • Michael Cahill

Posted March 09, 2008 - 12:31 PM


Thats what i'm thinkin too.

but i just dont want to have to replace the whole float if i have to, because this just started recently, and the bike runs perfect the way it is.

so is replacing the float an absolutly nessasary thing?
or can i just get away with replacing the gas tank valve?


  • dpast08

Posted March 09, 2008 - 03:44 PM


you're probably going to need to replace the needle valve and the needle valve seat. the rubber tip of the needle valve is probably worn. if you dont want to tear into the carb you should be fine replacing the gas shutoff on the tank and just turn the gas off after you ride. if it starts leaking more and more you are going to want to replace the needle valve and seat. check the float as well

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  • Michael Cahill

Posted March 09, 2008 - 05:41 PM


oh ok,

Im fine with tearing out the carb,
its just that the little needle valve is only sold as a set, and it costs $30 for the little thing.

i just am wondering if it is absolutly vital or not that the valve seats perfectly when ridding, i take it that it does'nt because i hav'nt noticed a change in the bike since it started leaking.

I'll just go ahead and replace the tank valve then.


  • dpast08

Posted March 09, 2008 - 07:00 PM


i had to replace the needle valve set on my 99 yz400f and it was around $45. if you dont mind a little gas dripping out while you ride you should be fine with replacing the valve on the gas tank. also check to make sure your carb isnt crooked. i had a ktm that was dripping gas and i realized the carb was angled slightly. once i straightened it out it was fine

  • USED YZ426F

Posted March 10, 2008 - 07:22 AM


I would replace both. Yes it will cost a few dollars, but if you only replace the tank petcock, you are only masking the real problem.
If you only replace one, I would do the float needle valve and seat, as this is most likely what is causing your fuel leak right now.
You can get the parts for about $45, and I'm sure cheaper if you shop around.
The tank petcock should be around $20 or less when shopping around.

  • Michael Cahill

Posted March 10, 2008 - 08:32 PM


ok well i'll go ahead and do bolth then, thanks for the help!


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