The /5 BMW is shown as an example, but this info applies to many models.
Just behind the BMW motorcycle engine and under the transmission is an area
that is sort of a "catch basin" or tray. It is best viewed from the left
side of the bike. I have no idea if this "tray" was intentional or not,
but we are glad to have it. It is an indicator of a possible problem.
It should be clean, but it is the place that will collect oil from an oil leak.
When cleaning the bike, spray some degreaser in there and run a bottle brush
through it to get it clean. It needs to be clean so that you can tell when
a new leak develops.
This photo shows a dirty bike that isn't leaking oil. You can see, but
not in this first photo, some dirt that has collected in a light film of oil.
The tray is directly below the transmission filler plug that is in the upper
center. That is a common condition, but it isn't a problem. One drop
on a hot engine will spread around quite well, collect dust and that is what
happened here. I haven't ridden it in two years. A few bikes will be
bone dry and while that is great, it is uncommon. Any amount that is in a
puddle should get your attention.
This photo was taken looking forwards and upwards towards the tray.
This hole shows no oil at all and is further evidence that this bike has no oil
leakage from this area. If the puddle tries to get really deep, the oil
will drain out from this hole at the rear of the tray. The day after a
ride, you will see a puddle on the floor, under this hole.
The oil can only come from two places, the engine or transmission.
Engine oil will have the normal smell and color of engine oil.
Transmission oil will smell bad, as it is what is called Hypoid gear oil.
If you are not sure, pull the dip stick and smell it, then remove the
transmission fill bolt and stick something in there for a sample and smell it.
You will detect the difference. A leak from the engine is more of a
nuisance than an immediate problem. If the leak is really bad, you must
replace the lost oil to keep the engine working.
If it is from the transmission, it may indicate a problem that needs
attention soon. A transmission leak is coming from the input seal.
It may leak because the seal is old or the input bearing is failing. That
bearing fails fairly quickly. Replacing bearings isn't cheap, but riding
until the gears are ruined too is very expensive. The oil from the
transmission input seal can also migrate along the shaft and onto the clutch
plate. It can begin the "slip" from oil. It is easy to clean it up
again, but requires removal to do it properly. A little oil getting on the
clutch plate won't slip, but get all gunked up and refuse to fully release.
When that happens the symptom is that it is hard to shift to neutral or first
when stopped. That symptom is the same as for a clutch cable with no free
play. Get free play at the clutch cable and test it again. When all
else fails, remove the transmission and clutch.
To fix anything in this area will require that the transmission be removed.
This is not a BMW clutch replacement procedure, it can be found elsewhere.
While the transmission is out, remove the clutch for inspection and possible
replacement. When I have it down to the flywheel I would also remove the
flywheel and changing the seal and oil pump cover O ring. That should fix
any oil leaking from the engine. It is too much work to get in there and
you are 4/5 of the way there, do it. You can also clean it up, as a clean
area is easier to diagnose next time.
Don't be intimidated by the crank moving thing. It is very easy to
prevent. It can be done in several ways. I have used a small block
of wood at the front of the crank and put the cover back on and loosely
tightened up the cover bolts. The block was thin enough that the bolts
would start and thick enough that they wouldn't bottom out. That way one
knows that the cover is pressing on the crank. In the shop we had a jig
(probably some BMW special tool that was inferior and over priced too) that
fastened on the front and held it back. Remember that it isn't getting any
great force trying to push it forwards. Only whatever force you put on it.
When a clutch plate wears, it gets tapered. The outer edge is thinner
than the inner edge. A new one is about .240" thick. I have seen
them wear down to .180" thick and that's the end, replace it. The steel
plates on either side of the clutch plate also wear and it's the accumulation of
wear on these three parts that causes slippage. The diaphragm, or forwards
plate, is slightly harder to measure. See my page on clutch service.
I have many times put a clutch back together with all used parts that are
still within my specs. They were not matched, by that I mean that they had
been in different machines and had whatever wear taper they had. They
quickly wear in together and work well. Break them in gently. A new
clutch should always be broken in gently, even with all new parts.
The fact that the crank moving issue isn't mentioned in some "BMW" workshop
manual is normal. I have commented many times what crap those manuals are.
That includes the BMW factory one too. I would venture to say that every
single procedure is written incorrectly, incompletely or fails to describe it in
a readable way. The /5 list is the best place to get both good and bad
info. You must sort it out.
I would be very suspicious of this post too. I hear that the writer
hasn't touched a wrench in 25 years, has white hair, is a cross dresser with