Cam shaft question


4 replies to this topic
  • A.Sailer95

Posted February 21, 2016 - 07:46 PM

#1

So I just rebuilt the top end of my 06 yz450f and fired it up and it ran for about 10 min then died so I pulled it apart again and the timing chain had a kink in it that I ended up being able to fix just by pressing on it with my hands. But now I'm putting it back together again and noticed that the lobes on the exhaust cam are way out of whack because usually when it's at tdc and timing is correct the lobes should be pointing outwards but I got the marks lined up but both the intake and exhaust lobes are pointing the same way. So clearly I need new camshafts now but my question is how did they get like that, and what else needs to be fixed/replaced so that it doesn't just happen again?ImageUploadedByThumper Talk1456112772.605950.jpg

  • Stevemeist

Posted February 21, 2016 - 08:07 PM

#2

If your timing chain is kinking you really need to replace it! I just rebuilt one for a buddy his chain kept slipping teeth because it was worn and stretched. Looks to me like same is happening to you.

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  • A.Sailer95

Posted February 21, 2016 - 08:18 PM

#3

If your timing chain is kinking you really need to replace it! I just rebuilt one for a buddy his chain kept slipping teeth because it was worn and stretched. Looks to me like same is happening to you.


Thanks! Any idea how the lobes would get shifted like that?

  • Stevemeist

Posted February 21, 2016 - 10:36 PM

#4

Your exhaust cam was the one that turned while the chain slipped on the intake cam. That's why it's out of time and why it won't run now.

  • grayracer513

Posted February 22, 2016 - 07:39 AM

#5

The sprockets are pressed on.  They very rarely slip, and almost never that much.  Usually see this sort of thing when a camshaft seizes to the head.  Any evidence of damage to the cam bearing areas? 







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