I own a 2000 400ex ( all stock except for uni filter). My bike starting smoking alittle and i dont know why. It only smokes when im on the gas , if i let the bike idel it wont smoke at all!!! My friends tell me that i got my valves adjusted wrong !!!
Do you guys think you know what the promblem could be!!!
Please Reply Back<===================HELP!!!

 

checking the valve adjustment is no big deal on a 400, if you have a manual it explains all the tolerances & how to do it.

personally i don't think its valve adjustment, maybe you cracked a ring, blew out a valve seal on your intake valve...
have you noticed any considerable loss in power?
" " checked your compression since it started?
also, what color is the smoke? white? blue? black?
-the color may indicate jetting needs changed.

maybe you just got some oil in the gas? maybe 2-stroke pre-mix?

 

Yeah smoke color will help. Black means your running rich in the carb, too much gas, white is burning oil. switch to a heavier oil like mobile15w50 or thicker. that will stop the smoke if it is white. Blue smoke its time to check the motor for problems. Blue is usually associated with water in the motor or sand

 

Its a four stoke dont premix. lol

 

What exactly is "white" exhaust? Everytime mine is started there is a whitish exhaust color, all cars in winter have a white color exhaust.... is there a special white that you are talking about that is like a "snow white"? just wondering.