Restoring a 1973 BMW R75/5 Motorcycle

February 24, 2007

Tool Time

Filed under: 1973, airhead, BMW motorcycle, motorcycle restoration, R75/5 — Penforhire @ 9:29 pm

Ed Korn’s tools arrived. Here’s the steering head race puller sort of assembled.


It works pretty much like I thought an “internally expanding bearing puller” should. The conical split washer on the right side goes under the race edge. Tightening the big nut pushes it against a ramped shoulder you can’t see, spreading that washer to get hold under the race. Then the metal sleeve fits on top of the steering tube and the nut-welded-to-washer on the left pulls the race out.

Here’s the end result.


One race on table. Flip the frame upside down then rinse-and-repeat to get the second race out. But I wouldn’t call it a true piece of cake.

To expand the split washer you need a 3/8″ socket on a long enough extension to reach through the steering tube. My 3/8″ socket happened to be for my 1/4″ drive ratchet so the handle didn’t give me enough leverage. I juggled a small cheater bar onto it (thanks Brad!). I also did not have a socket deep enough to fit over the big nut with the central bolt in place so I had to use a crescent wrench (metric of course) held at an angle. The metal sleeve has to be carefully centered around the top of the steering tube because its wall thickness is not enough to place it sloppily. It was about as awkward as it sounds but the important thing is that it worked! Also note the race doesn’t just break free and float out. It has to be pressed out all the way and the expanding washer should be re-expanded after the whole rig starts moving. Otherwise it has a tendency to pop loose. Ask me how I know.

Here’s Ed’s take on an adapter to get your torque wrench onto the four driveshaft-to-tranny bolts.


There is absolutely no room to get a regular wrench socket in there. This widget will fit easily over the 12-point bolt heads and the square drive fits a torque wrench that now has clearance. The only trick is accounting for the longer total torque wrench length by reducing the torque setting proportionate to its increased length from the center of grip (or pivoting force point if the wrench is otherwise marked). Yeah, I’m nowhere near needing this widget yet but I’ve got a drawer for special tools and it looks pretty in there.

This next tool comes unassembled and Ed’s instructions refer to it as an intelligence test. This is a puller for both the swing arm outer seals and inner bearing races.


If you can’t use the instructions to assemble it you probably shouldn’t be using it. I read the instructions a few times and something didn’t make sense so I went ahead and just did what he said to do. The part that didn’t make sense was assembling a nylock nut onto a short bolt and then “caging” it between the six screws and the metal plate. Here’s a close up of this part.


I had one of those “oh” moments when I figured out how it works and why he suggested lubricating the six bolt heads for smoother action.

This is yet another take on an internally expanding puller. The big set-screw-like bolt running through the center pushes the caged nut-and-bolt against the six screw heads and spreads them. Part of the tool set-up is making sure the six bolt heads are coplanar so they spread equally. The shoulder on the nut has a good angle to spread them. Ed must have spent some time figuring out the right lengths and bolt circle diameter to expand properly.

The outer swingarm seal has a soft rubber center which gets pushed down and then you expand the cage to trap it behind the seal lip. Place the cylinder (shown to the right) over the small bolt-plate and the base sits against the swing arm tube. Throw the larger plate on it (no threads, just a hole) to hold against the cylinder and use the nut-and-washer to drive out the seal. The central set-screw-bolt is long enough to repeat the whole procedure for the inner bearing race (after the seal and bearing are removed). Once again those races are press-fit all the way.

This tool is too cool. I wish I had thought of it. The small plate is also the right width to knock the replacement races back into position (after starting them in the tube with the larger plate). I’m not entirely clear on why the central section has a two-piece drive instead of just extending one longer bolt through the small plate all the way to the cage top (say two nuts locked together at the end). But again, this tool works! I was so glad to see the seals on my bench after they resisted my pry efforts. Take that you nasty seals, bwah ha, ha, ha, haaa!

I started cleaning the rear rim. I used Simple Green and a brass brush. This looks better but there are still many small pits that are black. I switched to a Scotchbrite pad and that improved things again. But I still have too many pits. I’m thinking I may need to try metal polish.

Along these lines I also started playing with some of the cast aluminum pieces. I tried some steam cleaning and Simple Green but these didn’t touch the corrosion finish. Did get some grease off though. I bought some Eagle One Etching Mag Wheel Cleaner to try but I’m afraid of it. No, seriously. This cocktail says it has phosphoric and hydrofluoric (HF) acid in it. The last time I played with HF acid mixture was about twenty years ago, mixed with nitric acid, I was wearing a Tyvek hazmat bunny suit and full respirator and the acid was raining down on me after exploding out of a barrel. We evacuated a few city blocks that day. Geez, sometimes I’m really happy not to be a junior engineer on a hazmat team anymore. Anyway, I am amazed they sell this sort of cocktail at Pepboys because HF acid is one of those uber-nasty acids that is only neutralized in the body by calcium…. which is only found in your bones. If it isn’t mixed with other acids you might not notice the burning hole. Okay, so Eagle One’s concentration is probably not that high but I’m still afraid of the bottle.

I also got the front wheel de-spoked today. For some unknown reason the spokes were considerably more frozen-stuck on the front than they were on the rear. I don’t recall if I mentioned it but the spoke nipples seem to be 5.4 mm (I have a real spoke wrench and, after breaking free, a 5.6 mm head works easier)… until you deform them. So what would someone like me do? Whip out a Dremel cut-off tool of course! Well, I actually had a hacksaw in hand before that thought hit me. Here’s the thing though. Some of those spokes are under tremendous strain. When I cut through them there’d be a gun-shot bang and the spoke head would shoot across the room while the spoke length would, often, shoot completely out the opposite direction. A couple of times I had to check myself, expecting to see a spoke head sticking out of me somewhere. Bad ju-ju. I did that to as few spokes as I could and worked the rest off.

While that does sound really stupid I did try to otherwise grab the stuck nipples to rotate them. The problem is the nipples are soft so they deform badly and shred under higher grip pressure. Naturally, once the hub got a little loose I had to grip each spoke with a Vice-Grip to prevent it from turning as I worked the nipple. Somehow the Vice-Grip bit me when I took it off one spoke.


Now I know you guys think this is a mighty small wound to mention but the moment I got pinched I said some words that people who know me don’t think I know. Oh, I know those words but I save them for occasions like this. Maybe I learned them watching my dad bust a few knuckles. Now the neighbor’s children know these words too.



  1. I’m afraid the bolt with the nylock nut is assembled backwards. The hardened bolt head should be in contact with the 6 screw heads not the soft nylock nut. Take another look at the drawing in the instruction sheet. “The part that didn’t make sense was assembling a nylock nut onto a short bolt and then “caging” it between the six screws and the metal plate.”

    Comment by anonymous — August 29, 2007 @ 12:30 am

  2. This post is great. thank you for sharing these helpful infos. I appreciate your work man

    Comment by aflam maroc — January 14, 2011 @ 3:39 pm

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