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MrYz400F

YZ400F Lots of backfire problem

4 posts in this topic

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

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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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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.

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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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