YZ400F Lots of backfire problem


3 replies to this topic
  • MrYz400F

Posted March 22, 2011 - 04:48 PM

#1

Hi, I have a 98 YZ400F And it's been sitting in my garage for about 6 months and when I got it running it runs good but just has a lot of backfire and I'm not to sure why. It's not just backfire it's loud pops. Please help. Thanks

  • ktmracer53

Posted March 22, 2011 - 06:05 PM

#2

Try adjusting the pilot screw. Put the screw all the way in and go out 2 turns, then just adjust it from there.

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  • grayracer513

Posted March 22, 2011 - 08:47 PM

#3

If it sat quite a while, it's likely that the pilot jet itelf has a film of varnish deposited in the orifice that is effectively making it smaller in size than it's supposed to be.

  • spdnjoe

Posted March 23, 2011 - 09:19 AM

#4

If it sat quite a while, it's likely that the pilot jet itelf has a film of varnish deposited in the orifice that is effectively making it smaller in size than it's supposed to be.


My 426 was doing the exact thing. I cleaned out the jets and it runs perfect. Even starts by the second kick with no choke !
Grayracer gave me the same advice a couple of months ago.
Thank you Gray !





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