07 yz450 bent intake valves

1 reply to this topic
  • mmccarth

Posted April 05, 2015 - 01:21 PM


So, scouring around a bit, it looks like I'm going to be out a pretty penny or parting out the bike but thought I would see if somebody had a different idea...


2007 YZ450f, engine unexpectedly completely quit while riding at a steady speed and kick starter was locked pretty solid (pushing by hand).   Yanked the engine and pulled it apart yesterday and first notice the intake cam was not close to the right timing when the cylinder was at TDC and then notice the intake valves were all bent.  Looks to me like a bit of galling on the intake cam where it rests in the cradle in the head (both on the cam and on the cradle in the head).  Pulled it all the way apart and obviously piston shows signs of collision as well.  Crank looks ok but from what I gathered reading and what I suspected, not very likely that it survived unscathed given that kind of a collision.  And, I'm still not 100% confident I know the true root cause of what started everything --bad oil pump? something that got in the engine or oil to start the galling and then had a cam seize and jump timing?


Pricing for parts or a whole complete used motor looks to be easy $2k not to mention complete bikes in this vintage selling for less than $3k.  Doesn't seem to pencil out anyway I look at it unless I'm missing an option on the repair.   Anybody see it differently? 

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  • Will.A.R.

Posted April 06, 2015 - 06:52 AM


Hard to tell from my phone but imho that galling doesn't look near bad enough to have caused the cam to seize. I also see oil on your cap so it appears at least some oil is getting to the head. Id look closely at the timing chain links and go from there. You didnt mention how many hours were on the engine. I look at it like this. If the rest of my bike is in excellent shape then I tend to fix/ rebuild. If you part it out and buy another, unless new, you may be buying a bike that could have the same problem 2 hours after u start riding it. At least if u build this one you know what u got.

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