R100s 1978 - Oil light only goes off at high revs

[gspd]

An oil pressure switch is only $25.
Try a new one.

[Rob Frankham]

An oil pressure switch is only $25.
Try a new one.

+1 on that... only... don't ride your bike to the store... It doesn't take long without oil to trash the mains and big ends.

Rob

[RPGR90s]

Just so you know, the Airhead oil pump is extremely reliable and well engineered, so most likely the fault is with the sending unit.

[gspd]

What grade and quantity of oil did you add?

Could be that the pickup screen on the oil pickup is partially blocked with sludge and/or debris.
You have to remove the oil pan to access it.
That could explain what you are experiencing.

[PAS]

You changed the filter then started the bike, didnt drive it, then shut it down until the next day, correct? The next day you rode it and the problem appeared. If this is all correct,you need to examine what you did during the filter change.

[daz]

Don't start it again until you find the problem!

[SteveD]

You changed the filter then started the bike, didnt drive it, then shut it down until the next day, correct? The next day you rode it and the problem appeared. If this is all correct,you need to examine what you did during the filter change.

[jackonz]

From what you have told us I would look at the following as I don't believe in coincidences especially when all you did was change the filter and oil.
First off is the oil the correct weight and so on.
Second is the oil at the correct level, check with the dipstick NOT screwed in, thread out.
Next check that you have fitted the filter and seal correctly, do you still have the old one and check it is exactly the same as the old one.

Last is a question, after you ran it the second time did you by chance re check the oil level and if so did the oil on the dip stick look frothy as in aerated oil, if so it is sucking in air and the only way that can happen as far as I can tell is from the oil pickup in the sump being lose.

[ME 109]

The o ring and shim is what I'd check. That's about the only place enough oil could be dumped to make the light stay on?

Pull the oil pressure sender unit and crank it, that will tell if there's oil pressure beyond the filter.
It might make a mess of course.

[Rob Frankham]

Fault finding list:

1. Obtain a replacement oil pressure sender and fit it. Start the engine and allow it to idle for a short time. Do not be tempted to rev the engine... most certainly don't ride the bike. If the oil light doesn't go out within 20 seconds switch off the engine. Don't start if again until the fault is located.
2. Remove the oil cooler adaptor and check the condition of the shim and 'O' ring (To avoid confusion, the shim goes in first, then the 'O' ring). Replace them if you are in the least doubtful about their condition. Check the oil filter. Some aftermarket filters have a bad reputation for collapsing and blocking the passage of oil. (Always use BMW OEM or Mahle filters (also may be found under the trade name Knecht which is Mahle)). This is also a good time to check the depth of the outer oil filter canister in the block. If you search this forum page, you will find dozens of threads about canisters being fitted at the wrong depth... it's unusual and unlikely in a 44 year old machine but a check to be made.
3. Remove the sump and check the security of the bolts securing the oil pick up to the block. (remove the spring clip and strainer to get access to the bolts). A number of people advocate wiring the bolts to ensure that they don't work loose.

If you've got this far without result, you are probably looking at an engine strip to get any further. Let us know if you need to go there...

Rob