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1972 R60/5

1972 BMW R60/5 (a.k.a. The reunion of a R60/5 frame with its engine)

BMW Repair Modification Restoration R80G/S R75/5 R100GSPD
This project actually started around March 2005 with the restoration of another bike, a matching number 1972 R75/5 . Unbeknownst to me at the time of purchase (seller was unaware), it must have had a rough life, because during a 2005 cosmetic restoration I found the frame to be bent beyond repair. It had t be replaced. The seller of the replacement frame (1972 R60/5) also had the engine short block and would have parted with it but money was tight on my end so I declined but asked for 1st right to refuse. Finally, in September 2010, I bought the block to go with the frame. So, technically, this bike is a Bitza: frame and engine short block from a 03/72 R60/5 (VIN #2942790), everything elso comes from a 02/72 R75/5 (VIN #2988429).

At the end of the season 2005 I had already decided to postpone the rebuild of the 600cc engine "until further notice" and put the bike in hibernation.

Fast forward to October 2012:
... the engine had be sent to Nathan at Boxerworks for installation of cam- and crankshaft, new oil pump etc. Many more green bucks were spent to buy parts such as cylinders, heads, rockers, pushrods, bearing shells, alternator, starter, clutch etc ... EVERTHING that you need to fill an empty block. I reckon, that I will have spent nearly $2,000 on parts and professional services for the engine when I am done. That of course does not include the hours that I will have spent.
September 2013:
Nothing really happening on this built: Spring came .. and went by without me touching the engine. The heads are still with a local guy that knows Porsche and Volkswagen, Richard is working an the modifiction of /6/7 rockers to my /5 heads. Other than that it has been quiet workwise over the summer. I hope my motivation will return over the winter and I can finish this up next spring ... should Spring ever come back!

March 2014:
It has been an exceptional winter: plenty of ice snow and in the last 8 weeks, only two days above 30F, otherwise mostly single Fahrenheit digits.

But it is now time to look over everything and finally assemble the engine.

Engine block:
Engine block modification: I opted to use the later front aluminum camshaft bearing flange (instead of the stock cast part). I also added two oil bores to the existing two in the process.

I bought the short block around August 2010 with crankshaft installed and original 284deg camshaft on the side. The blocks casting date is 03-Feb-1972. I bought a second early /6 camshaft short time after that I thought was in better condition as what I had. Engine block and camshafts were then shipped to Nathan @ Boxerworks to to have the the housing cleaned up, front bearing replaced and crankshaft play checked as well as a new oilpump (original Woodruff style) and used /5 flywheel installed with a new rear engine seal. As for the crankshaft bearing: the later design (slotted main bearing with the improved oil supply) was used to replace the original main bearing as the original main bearing is NLA.


Timing chain:
Timing chain modification: I installed the later single row timing chain on the inner set of the dual /5 gears. It allows the second set of gears to be re-used when the chain needs to be replaced.

New chain and guides were used. After inspection, both gears appeared to be usable.

Cylinders and pistons:
Cylinder modifications: large o-rings, piston skirt oil supply bores at bottom of cylinder

I bought 600cc cylinders from an early /6 ... so I thought. When they arrived they had a 99mm bore (indicating a '77 model) and a large o-ring, no grooves in bottom part of cylinders. Well, my thrusted machinist took care of that (reducing diameter to 97mm, adding groove and oil passages for piston skirts) and at the same time honed the cylinders to prepare for an engine run-in. I will use the high compression 0.020" gaskets.

They were completely refurbished by a local guy that knows Porsche and Volkswagen boxer engines very well: new seats, guides, valve springs and valves. Guides and seats are custom, valves and valve springs are Motobins (UK) recommended alternative replacement.

Valve train:
Valve train modification: valve train (rocker etc) were upgraded to the 76-84 design employing needle bearings. I am using the /5 heads with removable custom-made buttons supporting the indexing cutouts of the rocker blocks (helps eliminate axial rockerarm play). I used custom shims to adjust rockerarm axial play to 0.03 to 0.07mm: left intake needed 0.07mm, left exhaust 0.31mm, right intake 0.00mm and right exhaust 0.15mm.
The heads rocker posts themselves were not modified in the process

Engine assembly:

sprocket line-up

Worksheet cylhead


















torque scheme timing cvr














































Forks modification:
The original /5 top triple tree was replaced by a ToasterTan design. Because the original steering head bearing adjustment using a threaded ring and looking clamp interfered with the triple tree/tank, I used two steering head lock nuts back to back, one for adjusting and one for locking. This steering head bearing pre-load adjustment is now locked and will not be disturbed when clamping the top triple tree down or removing it later for e.g. fork maintenance.

Last time my Dad rode it in 2005 he complained about a very harsh front suspension. It was so bad that we swapped bikes on that trip around Western Ontario. Well, I looked at that first, here's what I found:

Yes, there is a sizeable gap between the fork brace and the fork leg whith the other fork leg being properly tightened. The gap surely accounted for the stiction that let to the harsh suspension. I had this corrected and it feels much better. Here are a couple of pictures from the "inner life" of a /5 fork:

I was working on the rear 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.

I also had a couple of thoughts on the handlebar switches and how we run 5A (60W at hugh beam) through them, all based on springs and funny shaped copper plates. Like a booster used on points (to prevent arcing) I was thinking of a way to reduce the load on those switches. I found an in-line relais, small enough to fit inside the headlight and with a 20A/30A rating that would be suitable to do this:

Search for "Micro Relay A/VFMA" to get the relay datasheet from the manufacturer (TE Connectivity).
Now, the stock /5 windshield is barndoor-sized and it is not my style. I like the Slipstreamer Spitfire windscreen and used it as a template to cut the barndoor down to a reasononable size. Came out really nice ...

This was supposed to be my classic Sunday afternoon ride but it turned out to be an engine project that went bad. First start to run-in the engine was ok but the alternator did not charge so the run-in was over after 10min or so, with bad noise from down below (right cyl I think). 2nd try (no changes made other than re-shimimg the rocker arms for 0.03mm to 0.07mm axial play): starter is turning just about, but engine is not catching, terrible screeching, sounds like dry metal on dry metal so I guess I must have clogged some of the oil galleries and the piston run dry in a dry bore. Or something else stupid I missed in the process.

Not having opened the engine I believe it needs a block, pistons/cylinders, maybe timing chain. I am sure the new heads are fine! The crank and cam shaft installation was done by a reputed shop in the US. I delivered an empty block and crank-/can shaft to them, they did the install. The shims were in place looking inside (pretty easy with an empty block). So I think I had the basics right. Anyways ... (you can feel my disappoinment here)

Sold as a (project gone bad) Oct 28, 2015

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