yz400 internal carb leak problem?

4 replies to this topic
  • KAM1

Posted August 13, 2010 - 09:46 AM


My cousin just got back into riding after a long absense, he bought a 99yz400, after purchase he realized gas was leaking out of fuel drain hose, sound like float or needle and seat issue, anyway he took it to a shop and they told him it had an internal leak and was a problem with these bikes and could not be fixed, any ideas? I live 8 hours away or I would figure it out thanks for any help, I am hoping to ride with him later this year and dont want him already discouraged.

  • grayracer513

Posted August 13, 2010 - 01:11 PM


Sounds like the shop didn't want to work on it. Your first inclination regarding the problem is probably correct.

If, down the road, the carb becomes a source of persistent headaches, and they can, have him replace the whole thing with a used unit for an '05 or later YZ450.

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  • number1sledhead

Posted August 13, 2010 - 02:38 PM


I found out a little more today. There are 5 seperate o-rings that seperate the body of the carb and the bowl. Some of them are circular, some are smilely shaped and others are oblong. One or more of these o-rings are leaking. The problem is that these o-rings are not available any longer.

  • KAM1

Posted August 13, 2010 - 04:38 PM


Orings are always available, you donkey(yep this is my cousin that I mentioned) afraid to get you're hands dirty. Just take them off and match them up, if you're not too lazy you could always drive up and sort through my selection,being an auto tech has its perk's.

  • grayracer513

Posted August 13, 2010 - 07:19 PM


If the carb main body has been separated from the upper float bowl at any time, you're probably hosed, regardless of what your favorite farm animal happens to be. Do not open that joint. If it's leaking from the drain hose, it's more likely the needle/seat, or the O-ring that seals the seat to the carb. Try that before you get too far afield.

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