07 YZ450F Cam chain

This is my 1st post. I have a 2007 yz450f that I was riding when it just stoped on me, felt like it lost all power. I Opned up the valve cover to check the timing and the intake cam spun on the sprocket and made the intake vales hit the piston. The chain did not jump because it was a TDC and the timing markings were correct. I looked at the otherside of my bike to look at my lobes that were facing out like they should but only my exhaust lobes were correct witch was at 2o clock. My intake lobes were at the 9o clock position when it should be in the 10o clock. Since the intake sprocket spun it made my springs work extra hard witch broke one of them causing no compression. my fix is buying a new cylinder since it was scratched, new piston, intake valves, springs, seals and 2 new cams. to never have this happen again I will be tigging the sprocket to the cam since its only pressed on. hope my hardship helps you.


When viewed from the LEFT side of the bike (the ignition/timing mark side), the exhaust cam lobes should be pointing at about 9 or 10 o'clock, and the intake cam lobes should be at about 2 or 3 o'clock, approximately. Basically, the exhaust points to the front of the bike, & the intake points to the back, with the piston at TDC. But the important thing here is that the timing marks are all lined up as they should be.

Also, check before you TIG the cam sprocket to the cam. that could (and most likely would ) screw up any hardness ratings/heat treatment the metal would have after heating it that much..... I do realize TIG focuses the heat in a small area, but I'd still be a bit leery about welding the sprocket to the cam. Seems like that's a sign of a bigger problem, actually..... :smirk:


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