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rezman

Cam cap question

5 posts in this topic

So..getting the money pit back together. Just received the cylinder head back yesterday almost $700.00 work. So a little nervous.... The intake cam was a little tighter to turn than the exhaust as received. Installed head torqued cam caps to 75 in lbs oiled threads and heads... I can turn the exh cam back and forth very easy, but the intake cam is tight. It will move but takes more effort. Valve clearances set by Fast Heads so that should not be the issue.

Should I pull it back apart? Should both cams turn with the same effort?

2005 YZ450 F

Thanks again

Ed

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Take the intake cam cap off and hit it with a little brake clean to get any oil off. Then you should get some decently fine sand paper and slowly start sanding the bearing surfaces on the cam cap. Wet sanding is probably you're best bet also. Be very careful to take even amounts of material off the bearing surface, and every once and a while you should put the cap back on the head and torque it on, then spin the cam and see how easy it is. After the cam spins relatively freely, get some aluminum polishing compound and polish the bearing surfaces. After they're pretty polished hit her with some brake clean and oil it up. Then install it back in the head and check how easily the cam moves. There should always be some resistance, but not much. And be VERY careful doing this. Too much clearance between the cam bearing and cam cap then the cap wouldn't be doing its job as effective as it should. Also a great idea would be to use some plasti gauge to check the bearing clearances. And lastly, while sanding, check how easy the cam spins relatively often, if you sand too much material off then you're going to have to buy another cam cap.

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DO NOT sand the interior of the cam caps. Ever.
 
It is normal for the intake cam to feel a bit tight; that changes as the head heats up.  What you should do if you think you need to check is the check the cam to cap clearance with PlastiGage per the manual.  It should be  0.0011–0.0024".  If the clearance is really excessively small, the correct way to deal with it is to polish the shaft itself, not the cap.  You can only do this with any real accuracy if a small amount of material is involved.  Get some 320 grit emery cloth and tear a 1/4" wide strip off the long edge.  Wind this one full time around the camshaft and polish the shaft using a pull-pull, "shoe-shine" kind of motion so the cloth cuts around the whole diameter at once. 

 

And only if it really needs it.

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Thanks again Gray... decided to pull the cam and plasticgauge it so I would know exactly where I stood.

The cam was not binding today, probably due to kicking it over without the spark plug to get oil primed.

The clearance came out within specs on the high side so glad I didn't start polishing materal away.

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Its alive.... got it all back together. A little hard starting but after making some adjustments runs sweet. Made a few passes down the street between the slush puddles. Lots of power...

Thanks again for the help.

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