Thread: CB desert sled
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Old 12-10-2012, 09:31 PM   #154
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Joined: Jun 2007
Location: Beaverton & Surrounding Areas
Oddometer: 2,237
Originally Posted by MortimerSickle View Post
I didn't keep track of the time involved, but once it got started it seemed to get worse at an increasing rate. I have no proof of cause, but this is a fairly common problem, at least on XRs, and the consensus on the XR forum seems to be that hard a aftermarket sprocket is the culprit.

I bought the bike used, and the sprocket that was on it was hard to get off. I didn't think to inspect the shaft at the time, but I think the damage had started with that sprocket.

After a season (two?) on the new sprocket, the damage was obvious, but less bad than in the below pic. I noticed the keeper had strange wear on it, so I pulled the sprocket, and found the damage. I foolishly hoped it would not get any worse, but after not-enough-hundred miles more, it looked like this.

I knew it was doomed, so just put it back together and kept riding. After an even shorter period of time it looked like it did in the first pic.

At that point I figured all was lost, and with nothing to lose, I welded the sprocket to the shaft to get some more mileage before changing the shaft.

The first sign of danger is a keeper that looks like this. But, I think that once the destruction starts, it will continue until it strips completely no matter what you do.

Though I can't be positive the sprocket caused this, I think it is likely enough to warrant never using aftermarket primaries again. The OEM sprocket for the XR is not only the proper hardness, but it also has a wider cross-section, or so I am told.
There also is no cush drive on XR600s or XR650Ls to dampen this kind of wear if the bikes are being used for a lot of street miles. I would love it if there were A) someone with a hardness tester to prove the varying hardness of the shaft and stock/aftermarket sprockets, and B) a more affordable cush-drive sprocket than the one made by RAD Manufacturing.

You're really going all-out by lengthening the frame, Luke. Great job. I hope to check it out in-person in a few months.
1982 4x4 longbed, a rolling daily driver work-in-progress...
1987 Yamaha XT600 2KF (German)
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