T H E  O L D  G R E E N  B E E M E R

Internally lowered front fork, ferrocement ship


Over 25 years and 100000km nothing much happened, regular maintenance was
to keep this thing going. Over these years regular maintenance included:

Piston rings replaced two year ago, together with a bore hone. New valves, new guides.
A few batteries where used over the 25 years, five (5) to be precise. Brands don't
say anything at all here. Number one an original German Bosch lasted a short
2 years ( top cover came loose ). Then two Mareg's, 5 years each. Next a
heard about Korean " Rocket '' brand managed to survive the
longest, 9 years. And now an XXX brand which is not great at all
years, and with health care so that is resurrected already.

Oil and Air filters,20W50 for the engine, advice* do not fill up to the top mark
otherwise oil consumption will increase. The engine cranckcase breathing
system on these types is a bit under dimensioned. best fill the engine oil
up to halfway the dipstick. For hot environment use maybe a larger oil
pan is a good idea as the original version does not hold a lot. For
colder climat use and short runs that's ok as the 1.5 to 2 liters
of oil will heat up a lot faster than the volume of the big pan.

Tires used, Metzeler, Continental, Heidenau. Spark plugs NGK, now using
the Halo Brand. Next, a
pair of Ignition contact breaker points, yes only
a pair.
I've kept the breaker cam oiled ( 20W50 ) and never filed or
sandpapered the points, they are still going today. Just make
sure the capacitor is alright and not corroded ( isolated ).
Take care that the O-ring of the ignition chamber is ok.
If not it can fill up with rain water ruining the points
and the mechanical ignition advance unit.

Then, Front Fork seals replaced twice. A new Ignition lock replaced
the1974 unit in 2019. That was about it. O forgot, fresh oil for the
80W90. Recently ( after the overhaul see below )
switched over to
85W140 hypoid oil for all tree of the trans -
mission parts. I've owned several / 6 and / 7 Beemers and
they all produced this typical gearbox rattle on idle with
a hot engine.
Now finally I can here no more rattling.

Just recently something showed up, gear oil started seeping out from the
Gearbox / Engine connection. Time to investigate: After taking the rear
end apart it was clear that the gearbox input oil seal was a gonner.
Being so close, I took the flywheel off to check the Crankshaft
seal... no leak here yet, but last year the engine started to
make the famous Turkey Honking sound, so the crank
seal is taking in air. Oil coming out will not be long
away, so work to be done. More than I expected.

Gearbox: All seals, all bearings and a few gear change outs.

Careful reshimming, more about that sometime later.

Engine: Crank seal replaced.

Clutch: No wear at all, still the original thickness unbelievable!!

Clutch actuator mechanism: New bearing and seals.

Splines: OK, no wear, used Molykote BR2 ( not according to specs )

Shaft: U joint becoming somewhat stiff, so needles beginning to deform,
no play yet ... Like to change the joint only, not the shaft, next winter.

Final drive, opened up: Crown wheel and pignon beginning to show wear,
seales replaced, ride on. I myself begin to show wear as well, also
ride on. The combined age of the bike and me is a 106 now.

As a bonus to all the work done: The honkingTurkey went away, gone!

I did not made a chapter about the transmission job and the makeshift
homemade tools
yet. If you like to know more about working
on the gearbox have a look at the links below.




Reverse mounted front and rear fenders.   Aluminum exhaust muffler mountings.
Earlobes welded to mainframe.   Rear brake actuator on foot peg.
carburettor intakes.
Saddle and rebar cargo rack. Stainless battery holder.
No speedometer. No rev counter. Better main stand. Stainless brake
Silicone brake oil. Slightly opened up exhausts. Balance
pipe valve. Air pressurized front fork. Outboard crankcase vent.
No problems points ignition. Homebrew fork oil. Special tank
filler cap.
Double electro pneumatic horns, LARGE sound.
Heidenau tires. O yes, a slightly lowered front fork and
 last, a reconditioned battery. Sure, it can be done.

Outboard crankcase breather and catch bottle, no more oil in the carberettor.
I like to install a pair of horizontally mounted bottles, in the open
between the fuel tank and cylinders, both sides, one fake ( toolbox )

And how it is hooked up internally, just turned the breather dome and
it down under a steel brace. I had to file two little grooves into the side of the
dome to give way for the bolts to pass, also, the original mounting lobe
you see up front was shaped down a bit for the cover to fit back on.

Gearbox breather, no more water in gear oil and ... no more speedometer.
After riding this bike for 3 decades I just about know how fast I'm going.
This ugly thing can be eliminated as well, more about it later on.
Still have to do the work on it.

Carb modification, I brazed some extensions on the adjuster screws to make
'm turnable by hand.
Now I can adjust idle and mixture settings while I am
sitting on the bike just by reaching down under and turn the knobs!
No more kneeling down into road crud ( ouch! ) and fumbling
with a screwdriver
unable to find the gap of the screws.

No more labyrinth seal but a standard item, no problem, just renew this thing
every other year or so. Much cheaper than new bearings.
span of the original labyrinth seal is about the same.

Saddle for the pilot made of Minicell foam covered in roofers gunk ( EPDM glue ).

The rebar cargo frame adds 8 kg of dead weight to top of the bike, now the bike
handles a lot better in strong ( side ) wind situations. Good!  On my daily
commute past the lake I catch a lot of side wind especially in the fall.
The extra 8kg bolted on dead weight trimming, makes a huge
difference in how the bike's reacts to that. Feels solid now.

Saddle for a passenger or cargo. Comfort for the passenger is ...
Between saddle and rack you can see a small air
for trimming front fork pressure, or tires.

Fork air tank filling and trimming valve.

Piping down towards the fork caps.

And into the fork legs, containing shortened springs for a lower ride.

I've done away with the O rings that normally seal the top ends as
they always damage when you take 'm apart. Instead I've used
LanoCote on the treads to make the assembly air / oil tight.
This product, used in the boating world is thick Lanolin
based substance, mainly used to prevent galvanic cor
rosion between dissimilar metals. The upside down
placed handlebar risers ... do the job alright but
I really schould make something more pretty.

Alternative fuel cap, German directions inclusive ( gas bottle item ).

Combined off the shelf brass plumbing parts. Note: the
thread is removed till halfway for easy insertion of the cap .

The Brass plumbing parts needed. Now find or make yourself something
to put on top of the square head to open and close the tank filling cap. Don't
forget to make a small air passage where rain water cannot enter into.
Here is where the gas bottle thing came to use. Additionally
 file or
grind a groove just under the upper rim of the cap for keeping
a big O ring, as well as a cavity in the inner threaded
part for the O ring to squeeze into and seal.

Like so. Green is the tank, Red is Epoxy resin. Note the small ventilation hole
the cap.The only downside of this setup I can think of is that the filler cap is a
loose item now, and can damage the tank paint if you manage to drop it.

Extremely good front tyre and not expensive, Heidenau K34. One hell of a good tyre.
Looks old fashioned just like the bike, but for me it makes all the difference in
handling and roadholding.
This is the best tyre I have come across in
decades. Very good for loose grit back roads and for highway use.
Inflate up to 2.5 bar at least, my advice; forget the 1.8 bar
inflation recommended by your bmw bike manual.

The same goes for the rear tyre, Heidenau K36, really sticky. Highly recommended.

Very similar in appearance to another famous German brand, Metzeler. The bike
handles a lot better with the K36, I never liked the Metzelers, way too hard and

I must say it again, this rubber is top, it's a soft compound, very
in fast cornering as well as heading in a straight line. Doesn't
make the bike jump sideways on loose grit. Just like the front tire
it feels very safe, also inflate up to 2.5 bar of pressure.

Get yourself Double disks, it's a Must have, make you live a bit longer.

Mystery valve, what does that do? I was curious to find out what the balance pipe
exactly adds to the performance of this engine, now I know ... a lot. Depending
on how far I close the pipe down, top end power delivery starts to melt away
big time and the bike starts to sound different as well. I have to see what
happens to fuel economy, my hunch is ... valve closed more miles.
Later I will try and explain the theory concerning the balance pipe.

High output voltage regulator, the so called "Police" version. The standard
unit is ok for summertime use, but if you like to avoid wintertime
sadness, you better change that one out for this one.

Drive Safe and Snappy.

Continue to Gasket / Liquid gasket

Back to BMW R 90/6 maintenance index / Home

MBP rev 2021

A A R D  V A N  H O L L A N D . C O M