4 replies to this topic
  • chunt450

Posted April 24, 2012 - 11:03 AM



Yesterday I was out riding my 2008 YZ450F and I laid the bike down doing a donut. The bike never shut off but when I got back on it and accelerated it began blowing white smoke from the exhaust. From what I could tell the smoke was white and it had kind of a burnt smell to it so I'm pretty sure that it is an oil issue. The smoke also lingers in the air instead of dissipating immediately. Could this be because when the bike was laid down the oil inside shifted and coated the cylinder walls?? Or is it because of a blown head gasket?? I recently changed the oil and put in 1.3 liters, could this have been caused because there was too much oil in the engine?? The bike does not smoke when it is idling but when I get on the throttle it starts and then progresively blows less and less smoke . . .[/size][/color]

  • briangriff321

Posted April 24, 2012 - 11:08 AM


White smoke is coolant so id go with a blown head gasket

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  • mrweehorn

Posted April 24, 2012 - 11:37 AM


have you still got good compression . from what you are sayin about the smoke lingering its definatly sounds like its burning oil. it could be an oil ring on the piston thats gone ,,,,, im not an expert though so could be some thing different.

  • yz450fcranker

Posted April 24, 2012 - 11:53 AM


get the engine fully disasembled to the point where you find the problem and get it fixed

  • grayracer513

Posted April 24, 2012 - 12:15 PM


To begin with, yes, you had too much oil in it, and yes, that will result in smoking. By the sound of the symptoms, I'd say you have a couple of valve guide seals leaking. Rings typically result in more smoke under a load, and the smoke won't clear up as you continue to run as you described. Valve guide seals will pump smoke on start up or as you first take off, and then the smoke will ease off after that.

Have a leak down test done for the information value of it. When you pull the head to replace the seals, you can inspect the bore at the same time.

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