Serious confusion with a 98 WR400

Alright my father owns a dirtbike shop. So a WR 400 comes in with a problem that we can't figure out. The problem is that the will not run once you shut off the choke. The bike will start normally but once it is warmed up and ready to go and you shut off the choke it stalls. The freaky thing is is that is stalls right out with no sputtering. My only idea is that there is something caught in the air passage to the main circuit in the caberator. I hope someone can help me out. Thanks.....

Check out Yamaha Tech Exchange M98-009. The description is "will not idle at any setting, check the adjustment of the throttle shaft".

If have a scanned copy that I can email you.


Also check the alignment of the throttle shaft with the end of the idle adjustment stop. The throttle shaft can be mis alignted horizontally and miss the end of the adjustment stop! So when you come off the choke circuit it transitions to a totally closed throittle. The throttle shaft horizontal slack is taken out via the set screw which holds the slide pickup arm under the carb top cover. The slide pickup arm is used to set the shaft end play.


Brian, is that the scanned copy you sent me a long time ago and I've yet to post it due to being way busy?

Oops! :)

I hope to get it on this week.



That be the one. I thought about telling him to ask you for it :)

I figured, nah, Bryan's doing such a great job with everything else on the site that I wouldn't push my luck.


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