Restoring a 1973 BMW R75/5 Motorcycle

January 25, 2007

The Pile of Knowledge

Filed under: 1973, airhead, BMW, motorcycle, motorcycle restoration, R75/5 — Penforhire @ 7:14 pm

Joe dropped by work the other day to loan me a wrench that might turn that starter nut. Check this out.


It took that nut right off! I haven’t tried it on the other side yet. I don’t think the handle curve was important, at least on this side, but it is a 12-point wrench with a narrow handle and shallow head. So imagine this.

He — “Honey, I need to go to Sears to look for ANOTHER wrench set that, uh, does what my existing wrench set does.”
She — “Didn’t you… just a couple of weeks ago…”
He — “No dear, those were sockets.”

Heck, I don’t even have a tool box to put another set of wrenches. So this is strictly loaner-tool time.

On the title of this post, there are several bookshelves where I work that Gary likes to call The Wall of Knowledge. It is a big reference section about the things we make. Well, when I first planned to restore this motorcycle, and as I ordered the Clymers & Haynes manuals, I scoured the internet and printed out every technical article I could find that related to this bike.

Here is a picture of what I like to call my Pile of Knowledge. It is about two inches thick and my home LaserJet groaned under the load of printing all this out.


One of the most prolific and detailed authors is a fellow named Duane Ausherman. His website is at but his articles are quoted all over and he is an active contributor on the 5 United board. He owned a BMW service shop in San Francisco and then, back when this old bike was brand new, he owned BMW of Marin. He tells us about things like incorrect factory-BMW service procedures.

So anyway, I skimmed through my pile of knowledge well before I started this project but I’ve been using the service manuals for this teardown. Most of the pile has to do with component repairs and restorations and I figured I would refer to my pile as I went through each stripped off section of the bike. But I re-read one article by Duane last night that drove me to write this mid-week blog post. Duane knows me. Not me personally but he clearly knows my type. Some day I would like to meet Mr. Ausherman and shake his hand. However I have the feeling if he knew who I was he would slowly shake his head and make clucking noises.

This article of his is titled, “BMW motorcycle exhaust pipes and finned nuts.” You remember my exhaust nut difficulties (if not re-read that post below)? Let me quote a few choice sentences from Duane’s document.

“There are two basic ways to get the nut off. Use a proper tool or cut them off.”

On the proper tool, “BMW had a tool made of cast iron. It was long and heavy. Many aftermarket tools have been made of aluminum and are lighter. They often break.”

Hmm, really? His favorite non-BMW version happens to be made by Ed Korn.

“There is a great risk that the threads will gall. They are aluminum against aluminum. If it seems to get tighter while rotating it off, stop. To continue is to risk ruining the threads on the head. To replace a nut is cheap but fixing the head is not cheap. The nut must be cut off with a hacksaw.”

Now you KNOW that I will never repeat my particular exhaust nut experience but I obviously could have avoided it if I had only read my pile of knowledge first. Oh well, nothing like knowledge learned the hard way, eh?

On the subject of where I am today, “It is possible to remove the head and send it to a number of shops that are set up to repair the threads…. The same shop will replace any missing fins for a small sum. At the same time you will want to do a valve job. Soon you will have hundreds of dollars in that head. All because you were too cheap to cut that nut off in the first place.”

Does he know me or what?! My only comfort is the path I travel was blazed by the stumbling of a thousand inept machanics before me. It is nice to be in the company of equals. I just wish they weren’t so clueless…


1 Comment »

  1. I had some real knuckle breakers on my engine too, including a couple of the starter bolts. Didn’t have a fancy schmantsy bent wrench but applied heat from a propane hobby torch for twen minutes and a socket with an extension and a wobbly took them out. Best advice? If it is supposed to stay put via a lockwasher, coat the threads with anti-sieze during reassembly. If no lock washer is called for (like those pesky driveshaft to trans output bolts, use new ones like you said, AND one single drop of Red Lock-tite on each during assembly. Red is supposed to be permanent and as far as I’m concerned, they’d better be. I had mine come apart at 60mph. Not pretty. A fellow lister from NYC was kind enough to donate a sweet low mileage comlete swingarm for the cost of shipping. I know that the red is not really permanent. I used it on the driveshaft bolts of our ’86 Mercury Capri and though I needed to use two wrenches (one as an extension) to remove them, they were removeable. I figure my driveshaft bolts will stay put.
    With either Lock-Tite or Nev-R-Sieze on the threads, the chance of galling (metal to metal stickage) is greatly reduced. I looked at those exhaust nut wrenches on the web and on ebay and ended up making my own. I severly croaked my original nuts by using a hammer and punch to remove/tighten them. I ground off all the fins after several broke off and simply used large water pump pliers but they were ugly. When I bought the replacements, I laid one on a piece of paper and dipping a 1/4″ bolt in some red paint, made a dot between each of the fins on the paper. Then I traced out the shape of the wrench. I put dots betwen the fins only a little over halfway around the nuts. I then used my paper template to mark out the wrench head on a piece of 1/4″ aluminum plate. I drilled the dots out with the correct drill bit size to tap the holes for 1/4″ bolts. Then I cut out the wrench head with a metal blade in my jigsaw. I didn’t cut it long with a built-in handle but i could have. Instead, I cut the handle short to a 1 1/2″ stub, about 1 1/2″ wide. I drilled a 1/2″ hole in it and used a triangular “rat tail” file to square the hole for my 1/2″ drive swivelhead ratchet. Works a charm. If I take it on the road, I toss in my shorty 1/2″ drive ratchet. Works for the ground down swingarm socket too with the addition of a 10″ piece of 3/4″ steel pipe as a snipe. The snipe doubles as a hammer as well πŸ™‚
    And Duane? Duane is THE guru man. He is like the Yoda of BMW motorcycles πŸ™‚

    Comment by Brent Schapansky — February 8, 2007 @ 8:40 pm

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