xr600 stuck rocker

Finishing up a rebuild. At TDC, cam lobes down. Rockers lifted up and valve cover on. You know how with lobes down the rockers should have some up and down wiggle? All but the right exhaust valve moves. This is the exhaust valve with the decomp. I even removed the screw and locknut and still no wiggle. I set valve tolerances to spec. Ive turned over the motor by hand and watched the cam actuate the valves. All seems normal. Sounds and feels. Yet at TDC i still have no wiggle on that rocker only.

Stock cam with decomp.

Last time i built an xr650l and put a hotcam no decomp and i dont recall this happening.

Thank you.


Unsure..The arm that works on that valve head inside the head cover is not somehow jammed is it..I know you said you had the rockers lifted up,,take it you mean you made sure the arms at the front inside the head cover that work on those valve heads were out of the way or lifted up as you dropped the cover on..They can get jammed specifically the manual decomp arm actuating arm one if you aren't careful getting the head cover on,,sort of need to hold them up with the fingers specially that front right,,it flops down rather easily..Only thing I can think off..not sure the head cover would go on if it was wrong..did you have trouble bolting it down Eric???


Whip the cover off and have a gander Eric..Make sure she's all still on TDC of the compression stroke when you finish up..T on mark..piston top of bore..Cam lobes down..Head cover on ..bolt her down (not excessive tightness on those small bolts) then adjust the gaps

Edited by Horri

Ok amateur move. Since motors not in frame i hadnt torqued my flywheel bolt down yet. So counter clockwise turns loosened the bolt. So to position crank i turned it clockwise. The decomp mech is a one way thing. So it was interfering somehow.

After i wrote that post i torqued flywheel bolt and turned it counter clockwise to observe my valvetrain. After a few rotations everything looked normal. I found the right exhaust rocker can wiggle now. So i readjusted the valve spec cause it was loose. And now everything's normal. So it seems. Still have more to do.

Dont find tdc by turning crank clockwise. It messes with the decomp. My manual and the internet were vague.

Thank you Horri. Valve cover stays on for now!

Turning the crank clockwise will indeed activate the decomp.........you must turn it counter......a few times arround,,,


Now,i`ve found turning just past TDC does a better job...keep lifting up and down on the right ex rocker while turning counter...just after you feel it click it loosens alot..a touch more and set em...the base circle is large...so passing the TDC mark is not an issue,,and is easier to set the right exhaust i find..



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