Breaking up on Wide Open

Finally got to ride this weekend. I notice the bike would break up on wide open then a small backfire when I let off. It seemed a little worse when I remove the baffle. I don't think it's the rev limiter. The only mods to the bike are a YZ throttle stop. All jets are stock and nothing has been changed from factory on any carb settings. The temp outside was around 60 and about 1000 feet above sea level. Could this be caused by being too lean?


how dirty is your air filter? mins pops on the run down bout a hour into an enduro coz it is restricting the air and runing rich.

The air filter is clean. It's still the original. I just turned 100 miles on the bike.

I agree with arrow, sounds a little fat up top. I'm assuming it's running fine everywhere else. Mine will do the same thing, in fact it was doing it yesterday. Reving it up, crack the throttle WFO, and start to cut out and break up. This will ususally load up my plug, and if I don't give it a chance at low RPM's to clear off, will foul. 99% of the time, if I go down a notch on my main, it will go away. I'm sure the smarter folk here may have a better idea.

Dodger :):D

[ April 08, 2002: Message edited by: Dodger ]

I think I may have cured the problem. I will do more testing this weekend. Real easy fix, removed the airbox lid. Hopefully this works.



I had the same problem until I did the usual mods. YZ timed. No airbox lid. No baffle. New jets/needle (to match all the above) That fixed the backfire for good. There seemed to be just a little of the break-up problem left until I cut the gray wire. After that I had no problems at all. :)

Tim Heslip

1998 WR400

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