Tight cam

I have a 2006 YZ450F and adjusted the valves. vales clearance is spot on BUT when I torque down the cap (10nm) on top of the cam the cam gets tight to the point that it wont move freely on the exhaust side. With no tension on the cam chain the intake side moves free, the exhaust side is tight unless I loosen the cam cover cap. 1/2 circlips are in the bearings, circlips slides into the groove in the cap and that should line up the cam in the head (journals) correct ?? It seems so simple, I don't see what I'm doing wrong. There are no marks or any issues with caps or the head, any ideas would be greatly appreciated.

Assuming that the cap is seated squarely (no debris, burrs, other damage causing it to tilt) and that you have torqued it in the correct sequence to the correct values, it may actually be normal.  I've seen several of the four-stroke YZ's in all sizes that behaved like that, including the YZ250F I owned. 


Check the clearance in the cap using Plasti-Gage as shown in the manual.  If it shows to be OK, then run it.  Remember that the head heats quickly, and that will loosen the cam bores as it happens.

I could understand if there was a little drag but this one doesn't budge at all, even when only torqued down to 3nm, intake side is smooth as silk. I'll keep playing and see what happens.

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