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1972 R75/5




1972 BMW R75/5 "The Heap"

BMW Repair Modification Restoration R80G/S R75/5 R100GSPD
I bought this bike in June 2004 for my father and put nearly 3000km on it in the first 5 weeks. It is running really well. Cosmetics and other stuff I leave for next winter, for now I'm ridin' ...







Start of Restauration in March 2005

Read on or fast-forward to May 25 ...

Now that the temperatures are bearable in Southern Ontario, it is time to start working on the R75/5. During the last years 3000km I noticed a couple of things I wanted to check:

So I decided to do a mild restauration and whilst going through the motorbike, change seals and gaskets where necessary, look at the problems and their possible causes. Before I started I had the bike running on the road to get the latest feel for it before dissassembly.

Shopping for parts

I went shopping for most parts at Motorworks in the UK:

Disassembly


It took me just 2 afternooons to disassemble the bike down to the bare frame. I took a couple of pictures of the inside of the headlight shell to be able to get everything back together to function as it was before. I considered that most of the body parts including the frame needed a new dress, so I will gather everyhing up and have it powdercoated, most probably at MES in Stoney Creek, Southern Ontario.

Initial findings after examination of all parts

Frame related work

I brought the frame to a guy near Buffalo, NY who was recommended to me my a fellow BMW rider. Once the work is done and the genius agrees to have his name and email published, I'll let you know.
Update: apparently somebody had already tried to straighten it and obviously failed. So it might not even be possible to straighten it after all and the expert has suggested not to throw good money after bad! So Plan B is in effect: use of a 03/73 R60/5 frame which I already purchased.

Gearbox related work

One seal and a boot need to be replaced in the clutch rod line up.

Timing Chain

Getting access to the timing chain is described in various articles at the know Beemer sites.

The procedure in short: get access to chain, remove old chain, fit new chain and get everything back together ;-) . The long version is described e.g. here and here.

Oilpan

Cleaning the pan and replacing the gasket are the two things to be done here.

Clutch Removal

Refer to your manual on how to removing the clutch. The seals and gaskets on the oil pump behind the clutch seem to seep a bit, therefore I will remove the clutch and replace all accessible seals.

Flywheel

In preparation, I secured the crankshaft with some cardboard between the front cover and the alternator rotor and produced a tool to prevent the flywheel from turning when removing the bolts.

Cylinder heads, barrels and pistons

If I remember correctly, one of the cylinders was weeping at the base and maybe at the pushrod seal. But really, that is only an excuse to open up and use all new seals and gaskets. So from here on, I know what is done and when.


Both pistons are Grade B pistons, 81.975mm diameter with matching barrels.

The exhaust valve relief of the LH piston is damaged. It looks like as if the exhaust valve had previously hammered on the relief. The exhaust valve looks brandnew so the previous owner seems to have corrected the problem.

Clutch installation

Refer to your manual on how to install the clutch.

I have bought a secondhand pressure plate and pressure ring with only little wear and combined that with a stock diaphragm spring (18mm) in good condition and a brandnew friction disc (thanks Rob @ The Five Workshop). Couple of minutes work (ok, half an hour) and it was done.

Tapered bearings

After having removed and cleaned the headstock and rear wheel bearings I have examined them closely. They show signs of pitting on the rollers and the races of the rear wheel bearing look as if installed with too much preload, they have notches. I have ordered some additional shims to correct the preload error and am buying the bearings at a local bearing supply. The rear wheel single row tapered bearings are marked "SKF 30203 Germany N+Z", the headstock single row tapered bearing is marked "SKF 320/28 X Germany-S M".
I have checked the front wheel bearings, they are in good shape with no signs of pitting. But since I could not access them for regrease, I decided to change them, they are only $32 Canadian. Here are two excellent articles on wheel bearings: Duane Ausherman's suggestions and Section 54 of Snowbum's technical articles. In Section 42, Snowbum elaborates on headstock and swingarm bearings.


Re-assembly

I follow a few simple rules when reassemblying that bike:
Stainless steel nuts and bolts:Wherever nuts and bolts are structurally important (shear or tractive forces at shock mounts, engine mounts, handlebar mounts, foot peg mounts, pinch bolts etc) I don't use stainless steel material for their material characteristics. If they are used for cosmetic reasons (just about anywhere else such as wheel covers, fender mounts etc), I always use copper-based antiseize to not get into trouble later with stainless steel bolts stuck in aluminium threads due to chemical reactions.
Rubber pieces:I have a shop locally which sells all sorts of rubbers, nuts and bolts (stainless too), even set crews for the tranny neutral switch fo a couple of cents etc (Spaenaur). I bought the majority of grommets and rubber pieces there as well. Even the ones on the batterie holder, the seat pan and thick M6 rubber washers for the fenders etc.

Things are coming together and I picked up all the parts form the paint shop. I will post pictures of the progress as I go along:

I had a bit of a problem when I started thinking about the wiring, namely about routing and connections on the ignition board.I found some very good information on the 5United group on Yahoo (thanks Nate, slash2nut and nsgreear) and have quickly summarized that on this webpage.


02/72 BMW R75/5 reborn as "The Blues"

former "The Heap"

May 25, 2005: here is the result of my nearly 2 months restoration:

Bike has been warmed up, so far no leaks anywhere, a longer trip will reveal any problems. Basically, everything is done, remains to have the VIN changed on the registration document.


Parts replaced during the restoration ...
Tools I have used during the restoration...
June 5, 2005:
We all have seen it before: ghost images when trying to adjust timing. The ignition timing was 2-3� off between cylinders on this engine and that was the way I ran all last year. Rather than fixing the probem which would mean measuring run-out of shaft and try to adjust or worst case replace (if it was bent) I decided to go for the alternate: fitting an electronic ignition with alternator rotor pickup which is what I had done on my '79 R100T just a couple of weeks before. Well worth the investment.
Result: very smooth running, brilliant starting, good mileage (42mpg average)
June 10-20, 2005:
5700km Ontario Loop 2005 Trip Report
June 24, 2005:
Now, here's the list of things that I encountered on the trip and which need attention:

Other than that the bike is perfect.
July 16, 2005:
Had a bit of time at my hands and fixed a few things:


November 5, 2005:
With the two ongoing projects, the
1982 R80G/S Paris-Dakar and the 1993 R100GS PD, I have decided to put the /5 to sleep for at least the 2006 season. Reason being, that I will use up all my time on the GS's. I read a couple of articles on how to prepare a bike for a hibernation and here is what I did:


November 2009:
The idea of getting the /5 out of hibernation crosses my mind ... and then disappears again! I was working on the shocks that I had bought: one was aftermarket and had what seemed to be progressives springs installed that I thought I could use. The second set was bought for parts as it had aluminum spring covers that were in excellent condition without the cutouts that I have on mine. So I thought I might as well replace the shocks (BMW OEM Boge part #1-0201-22-759-0 and/or BMW part # 1 230 274) while I am at replacing springs. I measured/calculated the springs using an online spring rate calculator:

I don't take those numbers as correct absolute values, but compared to each other are valid. Spring 2 appears to be softer from initial deflection. Both however are not progressive, just have plainly 2 springrates.


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