Darryl.Richman's picture

I was really hoping to ride the old girl out to the NorCal '49er Rally this Memorial Day weekend. The trip from Santa Cruz to Mariposa is about 160 miles one way and involves going over a couple pretty good passes (Hecker and Pacheco, the latter would require dicing it up with the trucks in the right lane).

Brent and I got the R52 back together again a couple weeks ago, and he told me to go out and "break it". I put about 100 miles on it, riding around locally so as not to require some kind Samaritan to have to drive too far away to come get me. But nothing broke, and things looked pretty good.

I have to say that stepping down a tooth on the pinion (from 13:57 to 12:57) seems like a good idea. In my informal testing, I could get about half way up a hill in 2nd that previously almost immediately required me to downshift to first. I also think I have the carb a bit better dialed in now.

In fact, it was while working on the carb and running the bike up and down the street in front of my house, that it felt like the clutch was slipping. That's annoying, because changing the clutch requires splitting the cases. (It wasn't until 1933 that BMW figured out how to leave the back of the bell housing open on the motor.) And sure enough, the next time I let out the clutch, the bike didn't move.

I looked down at it and was, therefore, quite surprised to see that the driveshaft was spinning! That meant that the final drive was where the slipping was occuring. I would have expected such slippage to be accompanied by really awful and expensive noises -- gear teeth chewing each other up. My new ring gear! My new pinion!

Once I had the final drive off the bike and apart, at first didn't understand what was wrong. No broken teeth. Everthing in proper mesh. Even the traces of Prussian Blue that Brent had applied were still on the edges, tops and bottoms of some of the teeth, showing that the shimming he had done was right. But on closer fiddling... err... inspection, I realized that the carrier, on which the ring gear is mounted, was pressed onto the hollow shaft that drives the rear wheel. And, "was" was the operative word.

The interference fit wasn't good enough, and now the inside of the carrier and the outside of the shaft were seriously galled. I left the parts with Brent after some discussion, and he said he would clean up the carrier and have the shaft built up, then turned down and both pieces polished.

But that won't happen for another week. I guess I'm going to ride something modern to the '49er.

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Was that just an interference

Jim Hansen's picture

Was that just an interference fit, or a shallow taper? It seems like a shallow taper would be better, but what do I know.

Although the shaft is really

Darryl.Richman's picture

Although the shaft is really chewed up, it seemed generally straight. A taper is very strong, but requires something to hold the two pieces together, like really big screw that holds the flywheel to the crankshaft on a /2.

--Darryl Richman
"Bling is not made in Germany" --OTL, 12/05

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