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Discussion Starter · #1 ·
I'm finishing up my valve adjust, and when moving the vertical cam by hand, it's movement isn't nearly as smooth as with the horizontal cam. I'm assuming that something needs to be replaced.

Should I look at bearings? Valve guides? How do I narrow down the problem. I have the desmotimes book, but it's been of very little use in diagnosing this problem.

TIA,
Adam
 

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Adam in MO said:
I'm finishing up my valve adjust, and when moving the vertical cam by hand, it's movement isn't nearly as smooth as with the horizontal cam. I'm assuming that something needs to be replaced.

Should I look at bearings? Valve guides? How do I narrow down the problem. I have the desmotimes book, but it's been of very little use in diagnosing this problem.

TIA,
Adam
Is it possible you have a tight closer? That would bind things.
 

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Discussion Starter · #3 ·
I guess it's possible that my intake closer is too tight, but I sanded it to about .0005" smaller than it was supposed to be (by my initial measurements).

I did replace the 1/2 rings though... how much of a difference is possible between worn and new 1/2 rings?

*the original 1/2 rings didn't look all that bad, but I figured they were worth replacing while I was in there, so...
 

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Adam in MO said:
I guess it's possible that my intake closer is too tight, but I sanded it to about .0005" smaller than it was supposed to be (by my initial measurements).

I did replace the 1/2 rings though... how much of a difference is possible between worn and new 1/2 rings?

*the original 1/2 rings didn't look all that bad, but I figured they were worth replacing while I was in there, so...
+1 on ducpainters recommendation. When I did my 851 there was a difference of a couple of thousand between old and new halfrings.
 

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Adam in MO said:
I guess it's possible that my intake closer is too tight, but I sanded it to about .0005" smaller than it was supposed to be (by my initial measurements).

I did replace the 1/2 rings though... how much of a difference is possible between worn and new 1/2 rings?
Yeah, there can be a difference there. If you were shooting for zero on the closer, it's possible the new half rings have eaten up all the clearance you thought you had. Check the closer clearances again...

big
 

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Both my 2000 M900 and 1999 900SS have "tighter" vertical head action than the horizontal. When I first noticed it I called BCM who told me it was fine. This was right after I sent my 900SS heads up there for port work and the tech who did the work said "normal". Subsequent to that I picked up a 2000 M900 with exactly the same symptom.
 

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Discussion Starter · #7 ·
in continuing to pursue the problem, I think y'all may be right... the closer shim is too thick. I'm going to progressively take it down about .0005" at a time 'till it starts sittin' pretty.

I also think that b/c you have less room to grab onto that cam it's more difficult to overcome the spring tension.

Will report back after the problem is all settled.
 

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You could just put the old half rings back in. The new ones are gonna deform until they look like the ones you took out and you'll be loose again.
 

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Ddan said:
You could just put the old half rings back in. The new ones are gonna deform until they look like the ones you took out and you'll be loose again.
But if you put them in upside down (they deform in one direction) youll be in the same situation.
 

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This is an interesting thread. I noticed that the vertical cams on my 916 engine were not as smooth as the horizontal head even after I did the adjustment. The clearances are good though as I checked them and the feeler gauge gave me .05mm on the closers.
 

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Discussion Starter · #11 ·
maybe b/c that head heats up more, there's more stress (and more deformity) on the components...
 
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