Restoring a 1973 BMW R75/5 Motorcycle

February 3, 2007

Walk toward the light

Filed under: 1973, airhead, BMW motorcycle, motorcycle restoration, R75/5 — Penforhire @ 2:21 pm

The bat-cave where I am working on this bike is lit by a 60 watt bare bulb over the washing machine in the corner. So when the sun sets I’m pretty much done for the day. I have some halogen flood lights but those things cast such bad shadows that I can’t figure out what’s what in that light. Gary convinced me I need to move into the modern age and add lighting to the garage. Friday during lunch he helped me bring home some Home Depot fixtures in his Explorer-that-will-not-die (211K miles and counting). We also hashed out how I should wire them up. Both of our houses do not have enough electrical service so the circuits get a bit tricky and we each have coping strategies. “Hmm, do I run the microwave, TV, and washing machine… wait for the microwave to finish before turning on the dryer… uh, oh, is she blow-drying her hair again…”

Naturally I changed my mind on wiring after getting parts for plan A. But Plan B worked better than most of my plans. Here are two of four twin 4′ T-8 bulb fluorescent fixtures I hung.

1791-shop-lights.jpg

The electronic ballasts fire these up instantly and it looks like daylight at the workbench at night! You might imagine this means I won’t have any more excuses for not working at night but you’d be wrong.

Bob read about my difficulties with the swing arm seals and he loaned me this.

1792-snap-on-seal-puller.jpg

Who knew that Snap-On makes a seal puller? I went around work trying to convince people its purpose was to kill chickens. Alas, when I got to prying with it on the swing arm seals this is what happened:

1793-broken-seal.jpg

Instead of levering the seal out it ruptured the seal edges wherever I could get enough grip to pry. Joe is thinking a mini pry bar worked for him in the past so I’ll be looking for an elf-sized pry bar soon.

Speaking of the swing arm, I thought I could go ahead and remove the drive shaft since the swing arm needs to eventually get powder coated or repainted. There is a 24 mm nut holding it together and the repair manual mentioned it would be tough to remove. The other end of the shaft gets locked in a soft jaw vise (that’s a towel in my bench vice to you and me) and then you just break loose the nut on the other end. Um, no, not quite. I put over 200 lbs at the end of my 18″ long 1/2 inch drive cheater bar and, while the vice started to splinter off the wood bench it is mounted on, nothing moved. Same for a little hammer beating. Grrrr. Joe says this is a tough nut to crack, so to speak. I’ll have to come back to it with some amazing cheater-bars-of-doom.

But the day was not all frustration. Check out another large hunk of bike removed.

1795-tranny-on-bench.jpg

That is the transmission. Yay! And remember that stupid neutral indicator wire that I couldn’t see how to remove? Well the situation got a lot clearer on the bench.

1796-neutral-wire.jpg

All I had to do was unwind a terminal-like set screw and the wire fell out through the casting you see at the bottom. Now why couldn’t either repair manual show me this?

This is a view of the clutch on the bike. I think there is more “bike” now on my shelves than on the frame so we’ll just say this is the clutch still attached to the carcass.

1797-clutch.jpg

Hey, I finally figured out how to pry out the gudgeon clips on the piston wrist pins. There is a small cut-out that lets me get behind them. I didn’t spot those before. So here are “the twins” on the bench. Meet Mr. Left and Mr. Right.

1798-pistons-on-bench.jpg

TBD if I can reuse them.

Here is the rear wheel, sans tire.

1800-rear-wheel-no-tire.jpg

Hard to believe some people change their own tires. Getting the old tire and inner tube off was a major pain, even using the tire spoons in the BMW tool kit. Heck, a fellow smaller than me would not have been able to break the bead. I had to jump up and down on it a bunch of times myself!

I started to remove the spokes and, prying on a weight, I managed to destroy my highest-quality flat blade screwdriver. No, really, this was a quality tool.

1803-busted-screwdriver.jpg

Monkey-boy strikes again. Can you believe there are still people willing to loan me tools?

I am not reusing the spokes and I still haven’t decided if the rim itself is salvageable. I had a rim crack on one of my cars so I know how alloys can get fatigued and self-destruct. I’d rather not have that happen when I’m riding in outer Kalamazoo, a million miles from home.

I got a lot done today but I’m still signing off early. Have to attend a “mother-in-law birthday party.” See you next time.

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1 Comment »

  1. Why are you replacing the spokes? Are they rusted? I thought that problem was solved by 1973!?!
    Anyways, those rims clean up really nice. Use some Fantastic or SprayNine, the wickeder the caustic, the better. Let them soak for about five minutes, then blast them with the pressure washer. Rinse them well and use some meguires or Mothers alloy polish. They’ll be so shiney you’ll forgive the dings. (Those just add character anyways 🙂
    Oh yeah, your alternator rotor, find a bolt that is same threads as the retainer bolt but a bit longer. Then find a piece of hardened steel rod that will fit easily inside the bolt hole, short enough to go all the way in and allow your bolt to thread in about half an inch. Slowly tighten this bolt down on the rod and prepare to catch the rotor as theu usually POP off suddenly!.
    And the swing-arm bearing seals? Take your second best (read: Dull) flat blade screwdriver and tap the Outer edge of the seal Inwards, deforming it and breaking the bond between the seals steel shell and the steel of the frame. When installing the new seals, tap them in evenly with a matching 1?2″ drive socket or seal driver. Give the steel shells a little swipe of grease first. Setting up the swing-arm properly is easy but must be done right or the bike may track funny and may even develop the infamouse SWB speedwobble!!!

    Comment by Brent Schapansky — February 8, 2007 @ 7:29 pm


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