Restoring a 1973 BMW R75/5 Motorcycle

January 28, 2007

It’s a grind

Filed under: 1973, airhead, BMW motorcycle, motorcycle restoration, R75/5 — Penforhire @ 4:15 pm

I rummaged around in the garage and tried a few things to grind that 27 mm socket. First off, and I expected this, the socket-plus-adapter was not balanced on a vertical drill press. I was smart enough to set a low speed and shut it off the instant after I turned it on. It immediately started to dance. Hmm, now what? Gary tells me everyone needs a bench grinder. Well my garage is small so I’m lucky to have a bench vise, so no grinder. I have some grinding stones for Dremel use. I chuck those up in the press and grind for a while. I guess they are not made to grind vanadium chrome-moly because it sure was slow going. I rotated it constantly against the stone to avoid flat spots and checked once in a while with a caliper for out-of-round. I switched to a drum sander attachment and that sped up the process to only an hour or two. The socket got too hot to hold in about ten seconds and then had to cool for about thirty seconds. Slow going.

And before you gripe at me about side-loading a drill press, this is actually an older Shopsmith (thanks Dan! long story but I bought it from Dan) designed for some side-load. The Shopsmith is perfect for me because it combines a bunch of power tools (I have fittings for a table saw, lathe, band saw, jointer, disk-or-drum sander, and slow router) into a small space. While it is sloppier than, say, a dedicated table saw it is a perfect match for my cub scout power tool skills. And I have some crappy hand-made furniture to prove it!

Here’s the finished product and it worked on the swing arm lock nuts. I used it on the end of an 18″ breaker bar I happen to have for 1/2″ drive sockets but I still needed to whack it with a hammer to get ’em loose! I think they were over-tightened.

1786-ground-27-mm-socket.jpg

Anyone know if chromed socket dust is hazardous? Because I sure got that all over. I’ll be pissed if I find out BMW sells a good tool for this for less than $10. Because this sucker was a lot of work to make

Here’s the drive shaft poking out from the swing arm on my bench.

1787-drive-shaft-swing-arm.jpg

Those four holes at the end of the drive shaft are where those 12-point bolts insert and screw into the tranny. See the pivot housing pointing down at the lower left of the photo? There is a grease seal on this that I cannot seem to remove. I want to examine the bearings trapped behind it. The manuals talk about levering the seals out with a screw driver (and they must be replaced anyway). But I grunted with various screw drivers for a while before I called Joe. His caller ID must be working because he didn’t pick up. Okay, put the swing arm on a shelf and attack it some other day.

Did I mention how nasty the whole swing arm is with caked-on road splooge? It is too rigid to wipe off and too soft to knock off. You end up scraping splooge shavings into an enormous pile. The old grease is fairly gross too but at least that is soft enough to wipe.

Here is the clutch release arm. It sort of hangs in the air between the tranny and the swing arm. The hook that captures the cable from the handlebar clutch lever is just out of the picture to the right.

1789-clutch-release-arm.jpg

I had to de-splooge it just to figure out how to disassemble it. The crud was caked so thick that it did not look like the part in the repair manual. Hey, that grease fitting sure looks normal to me (so what’s up with yesterday’s fitting?). That cotter pin at the bottom of the picture was completely obscured. Speaking of which, if you look closely you will see evidence that I’m not the only lame mechanic to ever work on this bike. That cotter pin was never bent! Hah! I found someone that I can make fun of. Never mind that I still had to use a hammer to tap it out…

Interesting. The tranny has its own oil. At least it was easy to drain. There is a magnetic drain plug but I don’t know how excited I should be about the fine black sludge sticking to it. Some metal filings are normal. Right?

Okay, I know I talked about the tranny being ready to drop but I’m not quite there yet. Soon. I still haven’t figured out how to disconnect the Neutral switch wire. It is stuck under a strange conical nut or some-such at the rear of the tranny. Both repair manuals say “remove the Neutral switch wire” but neglect to mention how the darn thing is attached. Oh well, worst case I’ll just cut it and stare at it on the bench later, since I plan on a new harness anyway.

I also should decide pretty soon on what shop I want to refinish the heads and cylinders/pistons. They are almost ready to ship. I think I’ll ask Irv Seaver and maybe Brown Motor Works, my two closest BMW dealers, if they do this work themselves. Joe gave me Bob’s BMW (http://www.bobsbmw.com) mail-order catalog and I know they do this work and even publish most of the prices. But shipping will not be cheap for all this metal. Any other independent repair shops near Los Angeles I should check out? Post a comment if you have a favorite.

I think Joe has a favorite local powder coater so I’m set there, though I haven’t decided if the headlight bucket (and a couple of other bits) gets powder coated or just re-painted. I also haven’t worked out how I’m removing and re-riveting the stamped information plate at the steering head. Buchanan Spoke and Rim (http://www.buchananspokes.com) is a nearby well-regarded shop that can re-lace my wheels (they used to refinish hubs & wheels too but recently stopped offering that). And I need a local chromer but there are a million platers in So Cal. I also need a shop to beadblast my aluminum bits (maybe the powder coater will do it or know of a good shop).

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2 Comments »

  1. Re: Your ground down socket, BTDT, LOL.
    As for getting that crud off, I cheated. All my small parts, wheel and swing-arm bearings, etc. went into a plastic tobacco can (any sealable container will work) and I poured in enough acetone to cover them, then swirled the closed tin. Works a damn! A careful rinse in fresh acetone and a quiock blow dry for the bearings (do not hold the center and spin the bearings with your air blower nozzle. Big time BAD for the bearings). I even chucked my old wheel seals into the acetone just to look for a number on them. The rubber (or whatever it is) swelled up hugely. After a couple of days, it sharnk back to normal and I reused teo of them as my new ones had been back ordered. They are still in the rear wheel and have not leaked any grease. I’ll change em some day, i promise! 🙂
    My clutch arm pivots were damaged badly (by me, don’t ask) years ago. One had to be welded back on. The holes were worn out in the pivot ears as well as the hole in the arm. I cut smallish slips of tin from one of those Littlefuse tins that glass automotive fuses come in. I curled it around the pivot pin, then inserted one piece inside the arm hole when reassembling. To fix the worn holes in the pivots, I drilled the holes out to match the brass bushings that came in a door hinge repair kit for Chrysler cars. used JB Weld to permanently bond the bushings into the holes, then drilled out the bushings to the original pivot pin size. Then, I found a bolt that was same size as the pivot pin and used it, with a flat washer on each side, and a Nylock nut to keep it all together. Tightened things right up again. I now use the grease zerk on that assembly for more than an ornament!!!
    Crap on the magnetic plug? If it has no noticably large chunks and feels smooth when rubbed between your fingertips, it is normal. Make sure to use a quality EP gear lube that contains additives to protect barss/bronze. I used Q-State full synth despite the horror stories of leaks. Guess what? NO leaks.
    For engine machine work, I use fellow listmember McMuck (Kelly McLaughlin) in Medicine Hat, Alberta. Whatever it costs to send your parts to a good shop, it is cheaper than sending them to a bad shop and sending the replacements to the good shop!

    Comment by Brent Schapansky — February 8, 2007 @ 7:48 pm

  2. most of the time, i would buy drill presses that are well built and uses ac induction motors -~*

    Comment by Natural Vitamins — November 24, 2010 @ 10:37 pm


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