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Jim_Bob

Inlet cam wont turn!

7 posts in this topic

I have just had my 99 Wr400 head tidied up but after putting the inlet cam back in and tightening up the cam cap I have found that it is almost impossible to turn. All the valves are in spec and the bearing is fine. You can feel a slight resistance with the cam sitting in its housing without the caps on- these seem to increase the problem. Has anyone had this problem before? Any advice?

Thanks, JB.

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Assuming it is the same cam that came out of that head and that you loosened and torqued the cap bolts in stages, I would suggest double-checking your bearing retainer to make sure it is fully seated in the groove. Also wiggle, turn and push the cam back and forth a little in the saddles before and while you seat the cap.

Is the cap seating flat and true without having to torque it? It should. A little tap with the heel of my hand seats mine flat and true and then I can finger-tighten all the bolts easily. Try installing the cam w/o the chain on to see if it will turn lobe to lobe each way. This is a wierd problem! :)

It doesn't make sense if they are the original components and no machining was done to the journals. The only mechanical reasons would be warped head, bent cam, mismatched journal sizes. If the head was not torqued on properly (in stages and evenly) it could be causing enough warpage to do this, I suppose. Aluminum warps easily if proper torquing procedures are not followed.

Post again when you figure it out. This is interesting, though I am sorry it is happening. Good luck!

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I have seen this a few times as well.

I tap the end of the cam with a deadblow or babbit hammer and that loosens the cam and allows it to spin freely.

This is the only plain brg in the engine and is sized pretty closely. It also is a point of seizure and will gall if it isn't spinning free. Mike atr engine dynamics also has the ability to repair this journal if it is smoked.

http://www.enginedynamics.com/

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Those bearing caps are very sensitive to improper torking-

the first time I did it I caused a little galling. I was lucky it wasn't too bad, and was able to clean it up enough by hand with emery paper and scotch brite.

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I ended up relieving a minute amount of the housing around the plain and roller bearings. This allowed the cam to rotate cleanly without the cam caps off. With the cam caps on there was slight resistance but it seemed to free itself once the cam chain etc. was installed. Amazing machines these Wr's- 20000 kms and rings, piston, cylinder and cam chain all still well within spec.

JB.

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Jim Bob,

Kevin can't be more correct, can't "star" torque the cap.

Have to follow the manual and torque from the inside out.

The only thing I can add is,,,when I rebuilt my engine this winter one of the valve caps were tight in the head. There must have been some debris that I didn't notice, it was fun getting the cap back off. The tolerance is very tight between the valve cap and the head. This is kind of silly to me because it is a none critical fit. But, Before installing the cams i depressed each valve manually making sure everything was free. Then I installed the caps and torqued from inside out and rode it for a couple hundred miles some in the beautiful state of Tennessee.

Good luck, don't overlook the obvious.

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