BMW R75/5, an all time classic

In 1969 it was the fastest serial motorcycle  


In 1989, after some years not owning a motorcycle, I bought a twenty year old second hand BMW R75/5. I used the Gummikuh (rubber cow) daily around Stuttgart. The longest trip I took it on was to Paris to visit a friend from the US, who was spending his holiday there. I sold the Gummikuh a few years later in dire need of money.Twenty years later I bought another one in the Philippines, still running but in very bad condition.

 Astrid with my first BMW R75/5 on Heinz' farm
in Germany
  Original condition of the R75/5 I bought 20 years later in the Philippines

The restoration took almost two years and was declared completed in January 2011. 


See the next pages for a restoration report.

Restoration Summary

The pictures below show that progress of the restoration, which stretched over almost two years because of repeated problems with spare part purchases and repair jobs of components.

 Condition of the Gummikuh in July 2009  The target, just in black
 September 2009, testing the engine after re-assembling it
 October 2009, the engine completely re-built, frame re-painted
but still waiting for parts
 December 10, 2009.  December 10, 2009. The gearbox still missing

30 January 2010: While still waiting for the instrument
in the lamp the R75 is assembled, the engine
tested and the carbs adjusted.

 There is still a lot to do, it needs a new exhaust, the original
round valve covers and a smaller back wheel. Original shock absorbers
at the back would also be nice.
(Click on the Photo for a big one).
 January 2011

 January 2011: Traditional valve covers, new exhaust
pipes from Polo, stainless steel battery covers, original
size back wheel, side mirrors, and
reconditioned carburetors.

 Restored original 750 ccm since the Siebenrock power kit with
1000 ccm was too much for the small battery and old
electric starter.



Finding a "Gummikuh" in the Philippines

In 1993 I had tried to import my BMW R80GS. to the Philippines but failed due to red tape and lack of clarity about process and cost. I tried again in 2004 but in addition to the shipping cost I would have to pay 100% tax, 30,000 to 50,000 Pesos (around 1,000 US$) for registration and an unspecified amount of grease money to various individuals who would try to take advantage of the situation. Not worth it. I subsequently bought a locally produced Honda XR200 and an imported Yamaha TTR250, which is excellent for off road trips on bad Philippine roads. So why considering a big bike at all? There are good reasons to get a bigger classic bike, even in the Philippines:

  • You can't go fast on Philippine roads because road conditions are really bad and traffic is very dangerous. Consequently a big classic bike with a big engine is ideal for relaxed cruising while Ducatis and Japanese rice rockets are pretty useless.
  • On the few tollways the country has motorcycles below 400 ccm are forbidden. 
  • The fund and show factors.

 So I was always on the look out for a BMW or a Harley. in 2009 I finally found several 2-valve BMWs that appeared affordable on I had a look at a BMW R100/6, which was according to the owner previously owned by a major of a major of a southern island. Despite the fact that the said major had some reputation for driving around with his motorcycle gang members and sometimes shooting at criminals taking the law in his own hand, the bike was in pretty bad condition, leaking oil in many places. In June 2009 there was a Triumph Bonneville advertised but I did not get any response from the seller when I emailed him. Later I found out that the owner was on trip. Shortly after I found a BMW R75/5 close by in Pagsanjan and had a look at it. It looked OK, was mostly original (so I thought) and the engine was running reasonably OK in idle and could be kick-started easily.

I thought it would not be a bad purchase for a almost 40 year old bike and agreed to buy it, intending to overhaul the pistons and cylinder heads and do some other minor work on getting it to original condition. I figured that although the old BMW was quite expensive (in Europe I would have paid a third of the price), if I would put another 1,000 US$ in some repairs, it would still be a lot cheaper than importing my bike and I would have two BMW bikes instead. The plan was to sell my Yamaha TTR250 as soon as the BMW is running well. How little did I know about the real condition of the BMW! It will take a while.

Driving home and a first assessment

During the test ride it drove OK, showing the typical local bike symptoms, the front brake handle could be pulled straight to the throttle lever without much breaking effect, the carbs were grossly out of sync, accelerating did not work because of a replaced throttle assembly and a screwed up gas cable, the engine did not rev well, but it seemed to have lots of torque at idle speed and the frame and gearbox seemed OK. Because someone had fitted custom shocks the back suspension was awfully stiff and each speed bump sent shock waves straight to my backbones.

When driving the cow back to Los Banos the first signs of serious engine damage became apparent. There was the occasional "clunk" sound from the engine, indicating a broken crankshaft bearing. At higher revs the engine lost power and was misfiring, and the valves made a hell of a noise once the engine got hot. Not so good. Anyway, I had a plan to overhaul the engine, so no big problem - I thought.

Before my home leave I took half day off work to dismantle the bike and identify broken parts, after all I was going to Germany where there are still lots of spare parts for the old cows. I already checked my previous contacts for spare parts from the BMW R25 restoration job, and found out that in the meantime even more small companies in Germany have specialized on providing spare parts and even re-engineered components for the old 2-valve BMWs at reasonable prices. 

But then, taking the bike apart was a bit shocking, I should have expected it because it always happens when I get involved with a newly purchased bike in the Philippines. As usual countless local mechanics had tinkered with the bike and made most serious modifications:

Engine and gearbox

  • The centrifugal timing advance was welded onto the camshaft. The engine could not be taken apart without further destroying the device and the camshaft
  • Crankshaft bearings and connecting rods bearings were worn
  • Exhaust threads are worn completely (which is sort of normal for a bike of this age)
  • Kick starter hung when operated and had to be pushed back manually
  • Main crankshaft seal leaked into the clutch compartment
  • Gearbox leaked at several places

Frame and suspension

  • Some metal triangles were welded to the frame to serve as seat holders for the third party single seat
  • The rear shock absorber bottom point was moved backwards. Probably because it is supposed to look cooler than a shock that runs straight down.
  • The battery holder was missing, instead the battery was placed loosely on a fiberglass fitting. One of the acid replacement openings was open, frame parts were corroded from leaking acid.
  • The wheel bearings were replaced, all fittings to adjust the bearings were taken out.The back wheel was ruined.
  • The swing arm bearings were also not original. The swing arm was very stiff.


  • Rear Handle and throttle mechanism was replaced and did not work properly, in fact did not work at all.
  • Switches in head light and at handle broken or missing and replaced with automotive switches
  • No air filter installed
  • No choke mechanism
  • The electrical system was completely screwed, no part original. Two diodes in the diode plate were burned, blinkers did not work, a complete mess.

I started realizing that there was  lot of work ahead of me.


More than 200,000 km?

According to BMW Sherb, who took the engine apart after we had shipped it to Germany, it had probably done a lot more than 200.000 km. Below are a few pictures of the wear.

The crankshaft




The major reason why I wanted the engine fixed was the "clonk" sound coming from the engine housing when the engine was hot, which indicated worn crankshaft bearings. In the old days one would have brought the crankshaft for grinding the bearings off to the next size and fitted oversize bearing seats, but because labor is so expensive in Germany it was cheaper to buy a new crankshaft.

 Wear at the floating bearings

Crankshaft bearing seats

   Heavy wear inside and outside the back and front bearing seat 


The bearing seats of the piston rods were also heavily worn.



Wear and pitting on the cams. 

The centrifugal timing advance was welded onto the camshaft. I had to use a grinder to remove it. It did not make sense to consider repairing the camshaft because the the cams were worn anyway but it shows how the local mechanics fix things. Instead of trying to do a proper job they usually use quick fixes that might help in the short run but cause problems in the future. 

Piston rods

  One of the piston rods had cracks in the eye and needed to be replaced too.

The oil pump

  As expected considering the overall wear of the engine the oil pump also had signs of heavy wear and needed to be replaced.

The electrical system

This was one big mess. After finding all the problems it was a miracle to me how the motorbike could run at all.



Restoration, the plan

The main points of the initial restoration plan:


  • Overhauling Crankshaft (in Germany)
  • Overhauling Cylinder heads (in Germany)
  • Instead of re-boring the cylinders, fit a Siebenrock power kit
  • Overhaul the carburetors (a gasket kit for each should do)
  • New right handle with proper throttle cables
  • Re-fit choke
  • New ignition timer


  • Sand blast and repaint the frame
  • Fit new seat for 2
  • Put rear shocks in original position

So I started to take the cow apart and with each part I removed it became clearer that it would have to be a full restoration job. Few parts were original. The ones still original were worn or broken. Once you have taken a bike apart to a certain level you don't want to put it back together with many of the parts not fixed and risk having to take it apart again the next year.

The big chill

Back to Germany

Well, the 2009 home leave was coming up soon. The idea to buy some spare parts in Germany actually helped deciding to buy the BMW quickly. But then, after realizing that I was lacking several special tools to take the engine block apart, I decided to take block and the two cylinder heads to Germany for overhauling. I had to go to a conference in Thailand first and alone I would not have sufficient luggage allowance I therefore asked Mavic and the kids to bring the parts. Together with a friend of the kids who was also travelling they were 4 and therefore had a lot bigger luggage allowance. I used found this old Zarges Box and the block just fitted in height. A few fittings made from wood and styrofoam to prevent the engine block from moving inside the box. The whole box weighed 34 kg and the two separately packed cylinder heads another 8 kg. Amazingly enough Mavic managed to get it through all the luggage scans and got it checked-in at Singapore Airlines without problems. 

Engine block repair

While everybody was complaining about the economic crisis it was extremely difficult to get an appointment with a workshop to get the job done in 3 weeks. Mathias came to the rescue and negotiated a time slot at Scherb in Groebenzell.They did an excellent job in the short time, sourced several spare parts that they did not have on stock and BMW could not deliver anymore and also overhauled the Cylinder heads. Just before I left Germany I could pick up the overhauled engine block. In the meantime I had also purchased a suitcase full of spare parts at BMW Bayer

Back to the Philippines, Frankfurt Airport and Philippine Customs nightmares

Traveling again separate from the family I brought the engine block per rental car from Stuttgart to Frankfurt. On check-in I was told that the Zarges box would not be accepted because it was too heavy. I was prepared to pay the excess but German labor law states that the airport workers are not supposed to carry more than 32kg so my 34kg box was rejected. I was very annoyed, I had handled the box alone all the way from Munich. The check in crew of Thai airways was useless and I was desperately looking for options: abandon the box - no way; call my parents to pick it up and ship it - also not feasible because they can't handle the heavy box either; call a friend in Munich and ask him to pick it up - one option, if I bring it to left luggage; cancel the flight and sort out shipment - not really a good option. Luckily a by-stander came to the rescue and pointed to a counter in the distance that said "Unbegleitetes Fluggepaeck". I had 45 minutes until departure and just managed to send the box via air freight at a cost of EUR 600.

Because the box came per air freight it ended up in the Philippine customs office in Manila and we had to clear it from there. Mavic and I spent a day, I rather don't report on the details, which included getting a huge number of signatures, a walk to a lawyer who certified that the engine is 40 years old and has no commercial value, customs inspection of the box and a major attempt to extract a bribe.

Revitalizing the heart of the Boxer

The engine block overhauled by Scherb with new crankshaft, camshaft, oil seals, oil pump, and piston rods. 





Assembling the cylinders was easy and straightforward.


Top view with one cylinder mounted.


I had not bought the tools needed for mounting the clutch. A whiteboard marker pen increased in diameter with scotch tape worked well for centering the clutch. Three long screws with a few bigger nuts and some washers did the trick to compress the clutch spring so that the remaining three screws could be fitted and tightened.

Then the big moment came. After mounting the electric starter it was connected with the battery, the crank case filled with engine oil and the oil flow to the rocker arms tested.

 Everything OK so far. The next task was to restore the frame.


Lito Diestro, a former IRRI engineer with a metal workshop in Los Banos, helped restoring the frame. He removed the attachments added for the seat holder, fitted attachments for the battery holders, and restored the mount for the rear shock on the swing.Finding a sandblasting shop in Manila on the other hand turned out an impossible task. After studying the yellow pages and consulting the Internet I finally found some shop where somebody answered the phone. Mavic and I drove there over a weekend and found out that it was not a shop but a backyard residence in a subdivision in Manila. The resident owned a huge truck mounted sandblaster, which was usually used to blast oil tanks in refineries. It was powered by a 12 cylinder diesel engine, a fuel guzzler. Since he did not have a job at the time he offered to set-up and run the monster for my tiny frame - at an astronomical price. I did not want to know what that sort of power would have done to the frame. Pajo, the husband of our former helper and a Jeepney mechanic, ended up sanding down the frame and re-painting it with epoxy primer and paint. After this was accomplished restoring the bike could begin.


It was quite a task restore the original condition because so many parts had been replaced by local parts of low quality and different design.

  • Front blinkers were moved back from the handlebar to the original position.
  • New rubber gaiters and battery holders were fitted. 
  • All wheel bearings, swing bearings and the steering bearings were replaced with originals.
  • The rear break pedal broken and Lito helped with a aluminium welding job to fix it.
  • All the old, rusty screws and nuts (some of them in imperial measurements) were replaced by V4A stainless steel screws and bolts.
  • The front light housing was fitted with a new combination instrument I found on ebay.
  • The back wheel was completely rotten. I had bought a set of wheels in ebay in Germany but they turned out to be both front wheels. I therefore converted a front wheel into a back wheel by moving the drive sprocket from the broken back wheel to the spare front wheel. 



Waiting for a gearbox replacement.

The gearbox also needed fixing. The spring that moves the kick starter back up in resting position was broken. There was also a funny screw at the back of the gearbox which leaked oil. When I removed the nut the screw fell inside the gearbox, so I had no choice but to open it. I got a special tool made to remove the driver flange on the output shaft but the damn thing was sitting so tight that three people and a 1.5m lever could not loosen the flange. Instead the tool started bending. Since it needs special tools to work on the gears anyway I decided just to buy a new or overhauled gearbox. Krystian knew a friend who had an overhauled 5 gear box at reasonable price so I bought it and got it shipped from Germany. Another 6 weeks waiting time.  On the positive side, I managed to sell the old gearbox for a good price on ebay during my 2010 home leave in Germany.


Volts and sparks

Nothing was original in the wiring mess (below). When ripping the old wires out I also found that two diodes in the diode plate were broken and part of its printed circuit board burned, probably by a shortcut. I wonder how the previous owners managed to keep the battery charged, probably by never using the light, the blinkers did not work anyway, and by kick starting the bike. That explains the broken kick starter.

From Germany I had already brought new switches and relays. But another problem was getting cables to re-build the wiring. Cables in Philippine electrical shops have very thick insulation and little copper inside. Detlef from Continental Philippines tried to help but they only have pre-configured cables and no bulk stock.Then I tried shops in Manila, with no success. Finally Tantan found a large variety of car wires somewhere in Manila and the wiring job could begin. 


 It took me two long weekend nights and half a crate of San Miguel to rewire the bike, as close as possible to the original but with compromises mainly on color coding of the wires.

 The ignition coils seemed OK, except that the original configuration contains two 6 V coils in series while my bike had two 12 V could parallel. This led to problems later with a weak spark on once cylinder so I swapped the two coils for a Rice Rocket coil with to secondary windings.  A concession to modern times, an electronic voltage regulator.

The "Bosch Erbsen" (diodes) of the diode plate I could not find, but other diodes with comparable performance, I therefore repaired the diode plate instead of buying a new one. Other work:

  • Replacement of the two capacitors in the picture by one as in the original.
  • New contact breaker.
  • New coals for the Alternator.
  • New breather hose in the contact breaker housing.


 The ignition/light switch was in poor condition but the basis was sound. A few new parts and it could be restored.  A new starter locking relay, prevents that the electric starter can engage while the engine is running.

 Not exactly as the original in appearance because of compromises in color coding of the wires, but functionally 100% the original.



Cosmetics and fine tuning

In January 2010 the bike was ready for test riding. Subsequently I did the following improvements:

  • Side mirrors from Polo, which look pretty similar than the original ones.
  • Exhaust pipes from Polo, cheaper than the Hoske and a bit more aggressive sounding than the originals





Soon to come

Before and after










































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