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bubbaisthebest

Is my yz400 in need for a rebuild?

5 posts in this topic

I got a 1999 yz400f during the summertime, and up until about October, it has run great. Now it is fouling spark plugs, 4 in three months, and it's not starting in one or two kicks like it usually does. I'm thinking that it's time for a new top end. Any thoughts would be appriciated. Thanks

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sounds like u have a jettin issue if ur foulin plugs...it ran great durin the summer time where its noticeably warmer. and now its gettin pretty chilly out now..yammies can get very touchy bout how its jetted durin weather changes

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First up I would check the valve clearances and give the carburettor a thorough clean out.

Hard starting is often a sign of tight valve clearances. The plug fouling could be due to your mixture being off.

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