Servicing the Slash 2 (/2) Oil Cleaning Slingers
© Copyright, 2011, R. Fleischer
slash2slingers-42
There
is very little Slash 2, or /2, information on this website. There
IS a listing of the rear drive ratios in one article,
ringgears.htm
The main reason there is so little /2 (and other earlier BMW
bikes) information is that my huge three ring binder of notes
'disappeared', and it was so many years since I worked on these
bikes, that I did not want to furnish possibly faulty memory
information.
Background:
Before the slash 5 boxer engine
motorcycle (which is often referred to as an Airhead) began
production in late 1969 (and that style of engine continued until
the end of production in 1995), BMW boxer engine bikes were very
different. The camshaft was located higher up, and
oiling was not the best. The location of the pushrod tubes is a
dead giveaway, as they are ABOVE the cylinders. For the
purpose of this article, I will use Slash 2, or /2, to include
all those BMW boxer engines that had no oil filter, but had
slingers.
Pertinent to this article, there was NO OIL FILTER such as a paper pleated filter, or anything even close to that, as there was on the Airheads. On the /2, the oil was 'filtered' by sending it into closely separated plates called slingers, where the harsher of the contaminants would be deposited into a relatively hard layer. The capacity of the cavities was limited. If the slingers were not cleaned at reasonable (you will NOT think the mileage reasonable!....30,000 miles!!!) intervals, the slingers would fill-up, and some very expensive engine parts would be destroyed.
In order to clean the slingers, you must disassemble the engine!
I wrote up an article on how to do this, and then saw a shorter article, more pertinent and to the point too!, posted on the Airheads List by Mike Arman, on October 11, 2010. I decided to edit it liberally, and post it here. While the information is reasonably complete on how to do the job, another reason it is here is to show you how much better the Airheads are, in having an oil filter!
To clean the slingers requires some special tools. You will
probably want to remove the engine from the frame. You will
have to remove everything in front, that means the magneto and
the generator. The timing chest has a lot of Allen screws,
and you must heat the cover.
You will have to remove the cylinders, pistons. You
don't even try to remove the rods at this point.
Removing of the large flywheel nut is required, locking the
flywheel (like one does with an Airhead) in order to undo that
nut.
You will be removing the oil pump drive nut which is a left-hand
thread, and remove the gear (on a taper).
You will rotate the crank and remove all 4 of the front cam
bearing housing screws, then heat the top of the crankcase quite
hot and remove the camshaft with the rear cam bearing.
There is a small bearing forward of the main crank gear; it needs
to be heated quite hot and then pulled off. You will have
to put the flywheel back temporarily and lock it again so you can
do the gear work.
You can then remove the front main bearing retainer...with a
heated crankcase. If the old style main bearing retainer is
cast iron, it may be cracked.
As Mike pointed out, for the R50S, R69, and R69S you'll need a special tool
which keeps
the self-aligning rear main bearing aligned. Fasten tool into
place, heat
the rear of the crankcase, pull the crank forward and "roll" it
and the rods out of the crankcase. Remove the rear main bearing
which had better be very tight. If it comes off easily, the rear of the crank is
necked, this can be fixed at high cost.
Now you can remove and clean the slingers. The deposits are HARD and
difficult to get completely out. It may be easier to buy new
slingers.
At this point you want to inspect
everything, and get new bearings (rear main is $$$). If you
use standard number 6207
for the main bearings, be sure they have metal cages and 11 or 13
balls...do not use plastic cage 9 ball bearings.
The other bearings, 60005 and 5204, etc., are not very expensive.
You will need new gaskets and seals, rear main seal, etc.
If the engine is
relatively worn, maybe you need to hone the cylinders, get new
piston rings, maybe even pistons. How are the valves, valve
seats, valve guides?
What about the generator brushes, ignition points, etc.?
Think about honing the cylinders, touching up the valve seats,
new
generator brushes, points, condenser, plugs and maybe wires.
Re-assembly is rather involved. Better get a good book. Mike recommended the BMW Blue Book manual.
Maybe you should be in
touch with Vetch!...and farm the job out...or?
rev. dates:
© Copyright, 2011, R. Fleischer