I remember reading something here on the throttle on a 400EX not being able to reach "full" throttle from the factory. If I remember correctly it has something to do with the thumb throttle assy. on the handlebars. My buddy has a 400EX, it runs strong, but I am curious if this is a problem with his. Any input would be greatly appreciated on this issue and how to resolve it. Thanx.

 

i think it has something to do with the actual thumb throttle on the bars.if you look inside the housing it looks like some sort of throttle stop.i dont know if it helps out if you cut that part off but i think the edelbroch carbs call for you to cut it when you run their carbs so the throttle valve opens fully.haven't tried on my stocker yet though.

 

Take the air filter hose off the carb. Push the throttle. If the float doesn't go all the way up and down out of view it needs adjusted. Pull the boot off the throttle cable loosen the lock nut and turn the cable nut out until you can press the throttle and have the float working all the way up and down. Mine had the same problem, I adjusted it and it really comes alive!!Hope this helps.