Info on 1951 R51/3 please

[stephan.pretorius]

I have a dilemma. Consider the fork assembly: The shop manual says part 14 (tube) should stick out 192mm above the fork bottom yoke (part 6). I bought a brand new set of lamp holders (part 1) and at the 192mm length, they seem to prevent the upper yoke (part 2) from getting sandwiched between the two nuts on the Damper picture (parts 6 and 7)...Is trimming of the lamp holders necessary to be able to pinch the upper yoke?

Please weigh in. With thanks,
Stephan

[rdnNHandAZ]

I bought the little wheel bearing grease tool from Dan at http://www.cycleworks.net/ I have yet to use it but I hope it works and I can grease the wheel bearings without future disassembly.

[stephan.pretorius]

An effort to replace the rear drive seals revealed much more than I was hoping to discover...

The cavity was filled with metal particles and the source for them easy to find - see the pictures. Based on simple mechanics, we know the smaller gear always fails first and it is clearly evident that it happened in this case as well. What is strange though, is the fact that the larger ring gear shows hardly any signs of wear.

The question is now how to move forward from here (I don't know how readily available there parts are:
1. Do I only replace the smaller pinion?
2. Do I replace the pair?
3. Any other reasonable options?

I attached pictures of the pinion with the damage and also the other relevant parts. The last picture shows the thrust bearing on the large gear impregnated with some of the grinding paste...

I would love to hear from those who had to rework the rear drive or those who have seen similar failures.

With thanks,
Stephan

[Darryl.Richman]

You should always replace them as a pair, they are lapped in together. Check with Vech or Mark Huggett for the parts. One thing that's nice about the /3s is that the ring gear separates from the drive splines, unlike everything newer.

[stwilliams]

All of the parts are readily available. You should definitely replace the gears. They come as a set as Darryl pointed out. It is important to shim the hole unit once assembled and check for backlash. I would suggest buying a gasket set too when you order the new gears. Hard to tell from the picture, but it looks like the spline still has some life left in it.

[Darryl.Richman]

Scott's right with his implication that there is some wear on the drive splines and that it isn't clear how much is there. If the splines still have most of their starting width, I would continue to use them and be sure to lube them lightly enough that it won't come off in use and contaminate the brake linings. I go with Honda Moly 60, but a similar lube would be fine, when putting the rear wheel back in place, and with each tire change.

[stephan.pretorius]

Thank you much for weighing in - I found the parts (now I only need the money). Is it fair to assume that a reputable BMW motorcycle dealership in the US would sell the same quality that I can buy from MH? Vech does not list the pinion and crown gearset on his pages - I will call him during next week to find out if he has any (not listed).

Splines on the wheel interface: I tried to take a good picture, but I was somewhat unsuccessful. The splines look good - minimal wear. Another enthusiast mentioned that for my use, they'd do well.

Scott I signed up to receive all updates n Weiss und Blau and I follow your postings often - thank you very much - your site very interesting and insightful.

I have one more question: the bell cover over the U-joint is a left hand thread. Is it a through left hand thread (ie. does it screw into the casing part with a left hand thread as well?

Thanks all!
Stephan

[Darryl.Richman]

If your BMW dealer is ordering the parts from BMW, then they are identical to what Mark Huggett or Vech would have. Mark Huggett has these parts made for BMW, and he and Vech have a marketting deal.

I would continue using your splines, but they are worn. You can see at the bottom of each spline how thick it was originally, and you can see that they are worn on both sides from that. If you investigate the inside of your wheel hub, you'll likely find tha the mating splines are also worn. If/when you do eventually buy a new set of splines, swap the front and rear wheels so as to get the "new" set of hub splines to go with the new drive splines; they will last longer that way.

The bell cover has a left handed thread, and the thread on the final drive casing is a matching left handed thread. (I'm not really sure what you're asking here.)

[stwilliams]

Thanks Stephen for the kind words. Glad to see you are back at it with the bike. If you still have a fair bit of parts to order, consider ordering from Germany (or Switzerland) as the prices can be considerably better than here at home. For sure Huggett has the parts. There are other sources as well.

If you utilize Vech for his expertise, knowledge and availability, then I would recommend buying the parts from him as he certainly earns his sales.

I too was baffled by the question on the bell housing cover. It is left hand thread, and screws on the the steel collar that tightens down on the pinion bearing in the housing. This too is left hand thread. If your steel threaded part is bunged up, these are available new as well.

Scott

[stephan.pretorius]

Having read my own posting again I agree that I wasn't very clear. The thread in question is the non visible interface (threaded) going into the drive housing - see pic