Boxerworks.com

My oil pressure light is coming on intermediately. It is a 1979 R65. This is my first BMW and my first motorcycle, but I assume this is the red light of death. A bit of history on the bike, I purchased it from the 3rd owner who put an amazing 500 miles on it in the last 15 years. I looks nice, but it has really just sat in a garage for awhile. Since I am learning to ride I have only had it out in parking lots and neighborhood streets at slow < 30 miles an hour. Today I took it out on the main road and was riding at 50ish miles an hour. After a few miles the light came on, I pulled off shut of the engine. Started back up no light, next stoplight the light came on at idle, pulled off shut of engine. Started back up no light, rode home light on then off while riding. Total trip maybe 7 miles. I have read that the sensor eventually leak, but I don't know if that means they also put out false positive or maybe false negatives . So the question is how do I fix this, or is this a rebuild the engine sort of thing. Also it does have oil (first thing I checked). Thanks, John

First thing first...don't drive/start the bike again until you figure this out. Could be a flaky switch, but I don't think that's very typical. So, you haven't done any maintenance like change the oil filter?? Starting with the '77 /7, BMW changed the oil filter system and if not done right, can result in loss of oil pressure and/or no oil filtration.

You should read this page:

http://www.largiader.com/tech/filters/

Carefully understand the section on canisters. You might find out how deep your canister is and then make a good choice for the metal shim (or protector), big white o-ring, and gasket. You most certainly need the shim and big o-ring...maybe you need multiple shims. The gasket is only needed if the canister is too close to the engine out case/surface.

Do some investigation and let us know.

Kurt in S.A.

I have done very little to the bike, and nothing engine wise. Thank you for the link to the oil filter page, I will order some parts and ensure the filter/ o-ring/ shims are as required. I will also take your advise and stay off the bike until I can sort this out.

John,

If you get curious while waiting for the parts you can inspect the O ring/shim/filter without draining the oil. Put the bike on the side stand with a couple of planks under the wheels so it leans over more than usual. The filter cover can then be removed with loss of very little oil.

Red light is charging system and will normally come on at idle rpms. If it comes on at higher speeds it could be worn brushes or a diode board on its way out, among other things. Oil light is yellow and can be tested by removing the wire from the switch and grounding it to the case.

On this bike both lights are red, the gen light does come on at idle, but unfortunately it was the oil light that was coming on.

Barry et al,
The good news is I pulled the oil filter cover as recommended and found a white o-ring and a metal shim. The bad news is when I measured the canister depth (tube to case distance) it was 4.12750 which indicates it should have 2 or 3 shims. I ordered some more shims hopefully this was this issue that I was experiencing. Thanks for all the help, I will keep you updated with the results.

John

Good job checking. Keep you're ear out in the future...hopefully no bad sounds!!

Kurt in S.A.

4.1 mm is very deep. I think you can be confident that is the cause of the oil pressure issue.

There are tales of the canister sinking further into the block with the type 248's (R45/R65's) so your problem is not unheard of. Hopefully it won't move again. Mine never has and sits at 3.1 mm.

By my reckoning you'll need 3 shims and no gasket. Perhaps the gasket was already absent.

Canister and O-ring Compression Formula

Using these specifications for replacement parts:
Metal Shim = 0.012” / 0.30mm
Paper Gasket = 0.018" / 0.45mm
Silicone Rubber o-ring = 0.158" / 4.00mm

BMW suggests an o-ring compression percentage of between 10% and 25%.

Formula to Determine Percentage of O-Ring Compression:
O-Ring (plus) shim (minus) gasket (minus) canister depth (divided by) O-ring (times) 100 = % of crush