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Yamaha WR400f poor/ no tick over

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Seem to have a fault with my WR400, bought as a non runner project.

Unable to obtain a tick over/ hard to start. Have had the carb cleaned untrasonic checked all the jets for size and blockage all seem ok. Removed the head re-worked the valve and rings hence good compression. I can only get it to run with the tick over screw wound in as far as poss this will give me an idle provided the pilot air screw is wound well out, but as soon as I use the throttle it just dies. Have moved needle jet up and down this gives me a clean throttle resonce up the range but nothing down low. any idea?

Will a different carb fit to try?

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Hi Eddie, will strip and check, seems ok as slide works well, when throttle scew is backed off it will close the venturi off complete. It almost seems like a large air leak causing weak mixture but have ruled out all possibilitys including vale guides, hot start, pilot air screw seal.

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Hi, Can someone confirm what slide plate square side down?

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Hi did you work out what was wrong in the end Ive got the same problem with mine exactly seems to be very common.

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