K75S Oil pressure light stays on after oil change

[detbmw]

So I bought my '88 K75S in September and it has been on a buddy's lift ever since. The drive splines were shot and I sent them to Bruno in Canada. Should have them back next week.

So, in the mean time we have flushed and replaced the coolant, replaced the fuel filter and fuel pump damper, sent the instrument cluster to Austin, TX to have the odometer repaired, and then replaced the instrument cluster and fairing. The back of the bike is still all apart.

So tonight we put the gas back in the tank and cranked it up and let it run for quite a while. Everything is looking good. Then I drain the oil, replace the filter, and add four quarts of oil. When we cranked it back up, the oil pressure light stayed on, even after a minute.

Did I break something during the change? The light was not on before the oil change.

[PGlaves]

Check the oil pressure wending unit wire under the little rubber boot at the oil pump at the front of the engine.

[jeff488]

Thanks, Paul

OK, I pulled the wire off the sending unit and the oil light went off.

Apparently the unit opens the circuit when pressure reaches a certain minimum, but I can't check that on the schematic because SOMEONE took the manual home with him tonight!

Is there a way to check the unit after removal? Maybe clean it or poke something up in it to free it up?

If you haven't guessed, the bike is on the lift in my garage.

[98lee]

Wending=Sending


If the wire to the sending unit is not the problem, I would suspect that there was a problem with your filter. Did the old filter o-ring come out with the old filter? If it stuck to the block and you put the new filter in on top of it, it would blow out allowing all the oil pressure to be dumped back into the sump.

DON'T RUN THE BIKE UNTIL YOU ARE SURE THAT YOU HAVE PRESSURE!!!!

Sounds like the oil pressure light is working correctly. Sounds like you don't have pressure. Drain oil, check filter.

[TED]

Did the old filter o-ring come out with the old filter? If it stuck to the block and you put the new filter in on top of it, it would blow out allowing all the oil pressure to be dumped back into the sump.

There is a thread here from some time ago with these exact symptoms, and this was exactly what happened. Matter of fact, Lee I think called that one too Now I always check the top of the filter coming out to make sure the o-ring is there. If it isn't on the filter it is stuck inside the engine and you'll need to get up in there to pull it out.

You might want to go back in, pull the filter and see if there is an o-ring stuck in there from the old filter, or even an o-ring from a filter from a prior change. Remember when putting a filter in, hand tight with a filter cup wrench then 1/2 turn with a socket wrench.

[jeff488]

Checked the old filter and it still has its o ring attached.

I suppose there could be one stuck up in there from a previous oil change , but wouldn't this symptom have occurred then?

I would think that those o rings stacked would blow out immediately.

I guess going back in is the next step.
But not tonight.

BTW, thanks for all the responses.

[detbmw]

Okay, the bike is running with no oil pressure light on!

Turns out someone (who will go unnamed but I believe he started this thread) fat fingered getting the new oil filter on and it was not seated properly.

Once again, thanks for the advice.

[98lee]

The reason I mentioned the possibility of the O-ring (even though it turned out not to be the case. But close) and why that is so deeply ingrained in me, is when I was around seven, I started holding the flashlight while my dad did tuneups and oil changes. By the time I was twelve, my dad would just tell me to go out and tune up the car or change the oil. Well, ONCE, when I was around thirteen or fourteen, I made the mistake of leaving the old filter o-ring in place. Luckily my dad didn't make it to the end of the driveway before the oil light came on.

Disappointing him like that because of doing a careless job (and probably the hours of cleaning the driveway) left a BIG impression on me.

[Rudyjo]

The reason I mentioned the possibility of the O-ring (even though it turned out not to be the case. But close) and why that is so deeply ingrained in me, is when I was around seven, I started holding the flashlight while my dad did tuneups and oil changes. By the time I was twelve, my dad would just tell me to go out and tune up the car or change the oil. Well, ONCE, when I was around thirteen or fourteen, I made the mistake of leaving the old filter o-ring in place. Luckily my dad didn't make it to the end of the driveway before the oil light came on.

Disappointing him like that because of doing a careless job (and probably the hours of cleaning the driveway) left a BIG impression on me.

Sometimes the best way to learn is to find out what happens when you don't do it right.
It helps to learn something the hard way sometimes.

[deilenberger]

Sometimes the best way to learn is to find out what happens when you don't do it right.
It helps to learn something the hard way sometimes.

Or "Experience teaches you things you don't want to know.." (I believe from Robert Jenkins..)

[jeff488]

OK, I'm real new to this brick thing, but learning quickly.
I can't help wondering why in the name of all the black forest elves do they run that filter inside an enclosed area??
The filter was designed to run external to an engine, so why go to the expense etc.
of designing and making a sealed cover for it?
The only thing that comes to my mind is that they wanted more room for oil capacity in the crankcase.
Unless it's just one of those Teutonic engineering deals.
Ready here for enlightenment.

[98lee]

The filter is inside the crankcase/oil pan, unlike most engines.

It's a packaging issue. They didn't want it hanging outside the engine like most engines because it would make the engine profile larger.

As an unintended benefit, it actually makes oil changes less messy if you do it right.

Instead of draining the oil through the drain plug and having oil dribble down your wrist as you remove the plug or have the plug fall into the drain pan, I remove the two filter cover bolts that are towards the right side of the bike. Then I SLOWLY loosen the third bolt to allow a very controlled release of the oil away from my wrench hand. You have to go in there anyway to replace the filter so this way you don't have to mess with the plug. It gets all but about a tablespoon of the oil out this way, saves on crush washers and keeps your hands and wrenches clean. And if you do it hot (like you should) it saves scalding you hands in hot oil.

[35634]

Good question. Could be esthetics (who wants an ugly randomly colored filter sticking out in the open) or space consideration. It is compact to put the filter in the sump, the only added expense is the access plate. I would like to know why they didn't put the head on the other side so the oil wouldn't drain into it when on the sidestand. The K's were a clean sheet design, so they could have put the swing arm on the other side and flipped the engine.

[TED]

The "K" in Kbike stands for "Kompact", which shares the meaning of the spoken word with English. It was revolutionary at the time, still pretty awesome if you ask me

[jeff488]

OK, compact design.
Why not then do it like on the oilheads?
Same filter recessed into the engine, but no cover needed..
This is probably nit picking, but still makes me wonder.
I like the oil change suggestion. Good thinking.

I like these bikes, and can see where they grow on you.
Sure runs smoothly, and this red K75S is a great looking piece.
Probably won't get one though, as I have enough bikes to fill the garage now.