09 yz450f smoking

6 replies to this topic
  • evanjensen242

Posted May 04, 2013 - 09:13 AM


so about 8 months ago i put a new piston/rings in my 09 yz450f and i didnt change the timing chain. well the chain slipped bike jumped time and did a number on my valves. i just put new intake valves, valve guids, springs, and seals and i went and rode it today and its smoking. the piston only has about 10 hours on it so i dont think thats the problem, its got a new gasket kit and the head is torqued corectly and im not loosing any coolant or oil. im basically out of ideas so any help would be great

Edited by evanjensen242, May 04, 2013 - 09:14 AM.

  • grayracer513

Posted May 04, 2013 - 12:02 PM


First, you need to determine if it's smoke or steam. Not too hard to tell. Steam from coolant has a distinct "peppery" smell, and disappears into the air fairly quickly, especially if it's hot out. Smoke doesn't vanish, it has to drift away instead, and will have a burned oil smell.

Oil smoke can only come from 3 places: rings, valve guide seals, or the head gasket. When you "did a number on the valves", did you check to see if any of the guides were loosened in the process? The bending may have affected them. Did you remove the cylinder and check to see if any of the rings are pinched in the grooves, or any other damage done to the bore?

Just some stuff to look at.

  • evanjensen242

Posted May 04, 2013 - 12:14 PM


I put new valve guides in it since one was cracked so i did all 3 the cylinder was fine and the rings were seated. And the gaskets and seals are new so i don't know how they could be leaking

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  • four-twenty-sixer

Posted May 05, 2013 - 04:04 PM


If your not losing any oil or coolant take a look in the muffler, the packing my be burning.

  • vic2340

Posted May 05, 2013 - 08:27 PM


In my opinion you should take the entire valve train and top end apart and examine them. The service manuals gives specs for each part within the engine so you should check to make sure all the parts are in the shapes they need to be as well as if they should be replaced or not. That's the only way you can find the exact root of the problem.

  • NitrousR1

Posted May 11, 2013 - 06:31 AM


Is it smoking while running or is it just smoking upon the first start of the day. If its smoking on the first start its valve stem seals. If its smoking while running chances are its your oil rings. One could have easily came out of its ring groove during install. Or the end gaps are aligned on the oil ring. Either the oil ring scraper or one of the oil rail rings

  • grayracer513

Posted May 11, 2013 - 09:31 AM


A more common error is to overlap the ends of the oil ring expander. Rolling a ring out of the groove on assembly is only possible with the oil rings, and the bike wouldn't run more than an hour like that before the cylinder was destroyed, if it even ran. Not really that much room available.

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