Matching Cam Sprockets to Chain?

[Guest]

I have an odd (to me) noise from the top end of my '80 GS850. These are the steps I have done to this point:
- had head done (new valve seals, exhaust guides, valves cut in, valve stems shortened to get shims in middle of adjustment range (2.65-2.75).
- ball honed cylinders and installed new rings.
- new seals in cam chain tensioner.
- rebuilt carbs.

When I was putting everything back together, I noted the one lobe of the intake cam had a crack in it, with evidence that it had been filed a bit to smooth off the crack edges, the crack was not on the top of the lobe bearing surface, but on the back of the lobe. I obtained a pair of cams on ebay, measured them to check wear, found they were better than my originals, and installed them.

I did not change the sprockets to my originals to match the cam chain, and now I'm wondering if the sprockets and chain are supposed to be matches, like on a drive chain.

The noise is a kind of rattling, and doesn't seem to affect the performance. I did not have this noise prior to the engine work...the only replaced major internals are the cams and sprockets. I've already done the recheck of the valve clearances after break-in, so it's not loose shims.

I even put in OEM exhaust gaskets, in case the Athena ones were not sitting properly...no change in the noise.

[Nessism]

I'd check the cam chain tensioner to make sure it's working properly. Noise from the chain interface to the sprockets seems unlikely unless something is significantly worn.

[49er]

Could be "cam walk". Your replacement cams may have greater clearance at the thrust rings than the originals. If the noise bugs you it can be fixed, if not just ride it as it won't harm the engine.

[Runningdog]

Well, as it turns out, this discussion should be in the "Stupid things you've done" thread.

Nessism, thanks for making me give my head a shake, and focus on the correct issue. Sure enough, my rattling noise was the cam chain tensioner....when I put the new seals in, I did not properly follow all the instructions (the part I got wrong came to me while I was taking the tensioner apart today), and apparently wound the spring up in the wrong direction. Of course, the tensioner would not tension when it was trying to pull the rod out, rather than pushing against the blade.

Silly bugger......works fine, now, the top end rebuild is as good as, or even better, than I hoped for.

Ride On