Restoring a 1973 BMW R75/5 Motorcycle

May 6, 2007


Filed under: airhead, BMW motorcycle, motorcycle restoration, R75/5 — Penforhire @ 9:31 pm

Here’s a lawn and garden tip. If you really want to kill some grass Engine Brite works amazingly well.


I was rinsing something a few weeks ago. Usually I work just on the bench or concrete driveway but for whatever reason I rinsed on the lawn. I don’t think my wife figured out why we got a sudden bald spot so, shhh! It managed to survive some unusually wet and warm weather so I’m not sure when I should expect green to return.

I’ve been thinking about buying a real tool chest for a while now. Here’s the $40 K-Mart special I’ve been working out of so far.


It is organized somewhere along the lines of knowing which pile to look through for what I need. And the 13 mm wrench always seems to be at the bottom of the pile. Anyway, this is the sort of decision I agonize over. I research this sort of thing intensely. Why? Dunno. I figure it has something to do with being a control freak and needing to KNOW I made the right choice, an informed choice. So anyway, I read everything I could find on sites like epinion, Amazon, other tool sellers, and various car club bulletin boards. Everyone has an opinion. Then I went out in the world and touchie-feelied. Then I ruminated some more on my needs and wants. Mechanic, to thine own self be true. Getting a picture yet? Well, I’m here to share my analysis with you.

At the top of the food chain are boxes made by companies like Snap-On, Mac, or Matco. Many (most?) pro mechanics swear by those but I can’t even pull the trigger on a set of Snap-On wrenches (at 10x the price of regular lifetime-warranty Craftsman wrenches). I’m not a pro so I just don’t need to pay that much. Below the top tier things get muddy. Most of the rest sell a range of quality from strong to weak under the same brand name. I’m thinking of names like Kennedy, Waterloo, Craftsman, Stanley, or Larin. Some brands, like Kobalt, get kicked around as the actual supplier varies from year to year.

So the next issue is deciding how big and what quality level.

Check out Sears’ Craftsman line for an idea how bewildering the choice can be. The offer at least four quality grades. The lowest is easy to throw out. The plain slides are not smooth even with nothing in the drawers and the sheet metal thickness is noticeably thin (weight rating is at least honestly low). Their next step up is Quiet Glide. These have plastic-covered rails for slightly smoother action and a little higher weight rating. The third grade is their ball-bearing slide with heavier gauge shelves. Their top grade, their “Pro” line, has additional features like shelf retention (so shelves don’t open unless you unlatch them) and even beefier casters and weight capacity.

And then you have to choose a size, not only width and how-high but also the arrangement of drawers (more drawers but smaller, fewer drawers but larger, or various mixes). Sears sells widths of at least 24″, 26″, 36″, 40″, 46″, 52″, and 56″. The bottom unit is normally a rolling chest and then you pile either a single “top chest” on that or also a third “middle chest.” Depending on the vertical height of each section you can end up with a tower above your head. I suppose choice is good, allowing you to fit the boxes into whatever space you have available in your garage and to only buy as much as you need and expand later. Me? Choice added complexity to the decision process.

I scoured the used market for a while (e-bay, Pennysaver, newspaper). Tool boxes are not a family heirloom thing to me. They are utilitarian. Oh, that also meant I wasn’t willing to pay a premium for a stainless steel finish. Plain Craftsman red would be fine. Unfortunately sellers of most good used deals are unwilling to ship them. Too much hassle to box and move such big heavy pieces. In too many cases folks bid too much at auction. Why pay 80+% of new price for used goods? I try to buy American where I can but I gave up on that for tool boxes. Most of the mid-grades and below are imports.

I have a hot tip for you if you really want to buy high end stuff. Find your local automotive trade schools and seek the student for-sale postings. The trick is, Snap-On offers a student discount of 50%. Students who wash out (or don’t survive?) their education are sometimes willing to sell boxes and tools at a further discount. In my case that is still too expensive.

At the low end, wait for a sale. This month Sears is selling a 26″ wide Quiet Glide rolling chest and top box combination for less than $300, a very good price. I just couldn’t come to grips with that quality level and I find their ball bearing and Pro lines overpriced. Lowes has a Kobalt ball bearing combo at a good price in stainless steel ($650 if I recall correctly) and I was impressed by the touchie feelie. Little things like shelf liners or other accessories can add up. Some come with, some without. Costco has a nice stainless steel stack with latching-handle drawers, I think 46″ wide, probably my #2 choice. But you’re never going to guess where I found my winner.

Harbor Freight. Yep, that sleazy den of substandard Chinese junk. I never would have considered looking there but a handful of people mentioned a particular item (see, item 90320-5VGA). Well I’ll be! It rates very highly to my touch. It has okay ball bearing slides, big castors, thick gauge metal, drawer retention, and locks. 44 inches wide! It even comes with liners and drawer labels. How beefy? The bottom chest weighs over 300 lbs while the top chest is around 170 lbs. The side handles are the only assembly required. Here it is in my garage. Note the R75 engine in front of it for scale. The stack is over 5′ tall.


Two deep drawers in the bottom section have double-slides.


I think it was Brad who mentioned tool boxes are where you slap on your stickers. Here’s an appropriate first one that I got for free at some show or rally years ago.


Hey! It doesn’t stick well to the textured finish. With matching top box this combo was $700, I consider that a real steal. If this wasn’t enough storage (it is for me) you can add a matching side set of drawers for another $200. There you have it, my best buy recommendation. What? Now you expect to see some work on the bike too? Okay, we’ll see if I deserve that nice tool chest…

In order to finish cleaning the transmission exterior I had to remove the kickstart and shift levers. Both are attached with an odd ramped pin, shove through one side and tighten a nut on the other.


They did NOT want to knock out. It took more than a couple of hammer strikes to pop them loose.

At some point while I’m working on the tranny and the engine work below, I realized I was in the zone, what is also called “flow.” Saturday my wife asked me if I was sore. I said no, why would I be? She said, because I was sitting in the same position for roughly eight hours working on bike parts. I had no idea that much time went by. Sure, I remember a bunch of different talk show hosts on the AM radio I listened to but I had no sense of the passage of time. From what I’ve read about flow it takes a certain minimum level of skill in the activity to allow consciousness to recede. Well call me Mr. Clean! My wife laments that I get no flow from household cleaning tasks and she most certainly does NOT think of me as Mr Clean. And until that brown spot turns green, the lawn still has a bone to pick with me.

Here’s the bottom of the engine, the oil pan.


Here it is again after several hours of effort.


Nice! Some of that hardened splooge absolutely refuses to budge unless attacked with a brass brush.

One of the problems with flow is that I forget to take enough photos for this blog. I made up for it with too many photos of the next steps. After removing the oil pan, here is the oil pick up strainer.


The screen is held on with that single wire clip across the face. After popping it off you can see inside the oil pick-up.


Then unscrew the two bolts and remove the pick-up. Hmm, there’s a gasket behind there. This is me scraping off the residue.


Now I have no idea why a gasket is needed at this location. If it was bolted together without a gasket, not as if anything that would get through the seam would be kept out by the strainer you see above. Damned peculiar if you ask me. Doesn’t matter, I am prepared with a new oil pick-up gasket.

Well, well. What’s that I spy up past the strainer?


That’s the camshaft! We have just seen one of the holier internal engine parts, something not meant for the light of day. I know, get over it. But seriously, I have never exposed the camshaft of anything I owned. I’d always figured that would be a bad thing. At this point I could also see the business end of the oil dip stick. Now, we all know how these things work but there is something visceral about observing the physical space it measures.

The oil pan gasket was a royal pain to remove.


I used some Permatex gasket remover spray, a nasty cancer-causing gel, after scraping off the bulk but this stuff was very resistant. Unlike my disposable nitrile gloves. Ate them in a heartbeat. You may notice I’m wearing gloves in many photos here. I sort of got smart. If I wear these gloves the clean up work is much easier since grease doesn’t get all over my hands and under my nails, just way up on my arms. But what happens is, I’m doing great until I take a break. Maybe going out for a tool, getting a drink, or whatever. Then there seems to be a need for me to touch things before I’m gloved up again. I can’t explain it. Sort of a Murphy’s law of grease. But if I ever get more disciplined these gloves will do the job.

I had to resort to some fine-grit sandpaper to smooth the pan sealing surface. The manual calls for adding a sealant on both sides of the replacement gasket. The original sealant must be something special.

Here’s a view of the sludge built up under the clutch.


That’s a small screwdriver you see me scraping with. I have a variety of scraping tools but I found a certain screwdriver to work best without scratching the motor’s alloy.

I actually got to working on the clutch today. Woo hoo! Before you take apart the clutch you’re supposed to mark across the pieces to preserve balance on reassembly.


This assumes the assembly was working well, not vibrating, to start with. I don’t have a clue if that is true but I’ll pretend it is for now.

The service manuals have dire warnings about the clutch spring and how it may kill you if you just free up the clutch bolts. Peak spring force is somewhere around 400 lbs! Both manuals call for pulling three of the six bolts and reinserting special tools, the correct BMW tool or home brew variations, to effect a controlled release after removing the other clutch bolts. Oddly enough, Eurotech sold me a pair, not a trio, of such devices.


I figure others have gone before me and survived. You wind the thumbscrew in and then spin the long threaded nut down to secure the clutch. After backing out the other screws you use a wrench to gently unwind the nuts, I used one turn per side, and release the clutch. I was a bit skittish and stood to the side while the spring made scary noises as I unwound the nuts.

I should mention one more thing about removal. Getting the clutch nuts loose is tricky. The engine spins freely, much easier than the nuts. One manual said nothing about this. The other recommended an impact wrench. Here is my unauthorized technique. I can see you cringing now, especially because, somewhere, I have that impact wrench Brad gave me…


This is a screwdriver jammed into the teeth of the flywheel. It probably was not the smartest solution but it worked and it didn’t break my flow. After loosening one screw I was able to use the screw hole to mount a proper jam for the others. I have a picture of that jam technique below (used again for flywheel bolts).

Here is the disassembled clutch. The parts stack in the assembly from upper left to right then lower left to right.


There are a bunch of wear and damage checks to perform. My parts are a bit rusty but the wear portions are well above replacement thickness. I’m a little uncertain about the spring. This is me measuring the free height with a caliper (I don’t own a depth gauge) down to a plate of glass. This is an indirect measure of force. Lower free height means less compression in use and that equals less force.


The free height measures about 17.5 mm. Book specification for the R75 is 18.5 to 19.5 mm. My spring would measure correctly for the R50 (weaker clutch spring). I got the used spare spring from Joe’s pile of parts and checked it. Measured about the same as mine. Curious. I called Joe and asked him if that spring was working okay when he sourced it. He said if it didn’t work it wouldn’t be in his spares. That’s a good philosophy! That also gives me some confidence to reuse mine. The other checks are okay (e.g. coplanarity of the spring arms). Any comments from other BMW experts?

Here is the flywheel still attached. Any time the flywheel bolts are loosened they have to be replaced. Special stretching bolts.


While we are on this subject, I have massive disagreement about the bolt torque specification. Normally I trust Clymers’ manual more than Haynes. Clymers says to use something like 50 Newton-Meters. Haynes says BMW changed the specification later to 125 Newton-Meters (!) because some bolts got loose. That is an absurd increase in tightening torque and I don’t trust it. I figure 50 NM was about right for the force it took to remove the bolts. At the end of today’s work I remounted the flywheel using about 75 NM and I’m going to see if I can find other references before twisting any more.

Here’s the anti-rotation widget Joe loaned me.


I had to mount it differently than its design for the clutch (supposed to mount from one clutch bolt to another). The dimensions match a template in one manual but would not work as intended, to jam against the engine casting. Meh. This technique worked and my flow continued.

Here is what things look like behind the flywheel, before cleaning things up further.


I believe that plate at the bottom is the cam cover. One possible reason for extra scuzz in this section is the cam cover had one loose phillips screw. There is a polymer seal to the back of the flywheel but it looks in good shape.

Well this is as far as I got this week. Not too shabby. Go forth and flow.



  1. I’m trying to get the shift and kick start levers off of the trany of my ’73 R75/5.

    I got the pin out of the shift lever (after quite a few whacks and liquid wrench), but haven’t been able to get the shift lever off yet, nor the pin or kick start lever.

    Any advice for me?

    Looking good!

    Comment by David — May 12, 2007 @ 6:35 pm

  2. Once the pin is out there is nothing but corrosion preventing the lever from sliding freely off the spline. Try some liquid wrench around the spline and maybe tap it down slightly to free it? My other ill-advised technique would be to try heating the lever but not the spline (to expand it slightly) if tapping doesn’t work.

    Comment by penforhire — May 13, 2007 @ 12:39 pm

  3. Your ’73 is looking great! Thanks for the info on the horn switch especially the images… excellent!
    Best wishes on your project…!

    Comment by Bill — July 13, 2007 @ 7:32 am

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Blog at

%d bloggers like this: