Oil Pressure Light

[zuluwiz]

Got out today for the first time this year. I parked the Ratzuki back in August because the oil pressure light was flickering at idle. Someone told me it was probably the sending unit (switch) that was bad and I should just ignore it. Didnt seem prudent to do that but when i finally got it started up and running, there was no light on. OK, I took it out for a short (25 mile ) run and now it's on at medium revs,(4000/4500) not flickering. The bike ran strong, didn't miss a beat. This 81 GS850 has 20k miles on it, a new battery, new stator and R/R (sh775) and seems ok, but I hate not knowing the problem with it. Any advice?

[Rich82GS750TZ]

Have you cleaned the electrical connections? My bike has a wire with a lug that bolts to the sensor on the oil filter cover and a bullet connector where it plugs into the harness near the battery. Then check continuity as both ends of that wire. Not sure about yours. Suppose it could be a faulty sensor. Check the archives and see if anyone’s had a similar issue?

[Redman]

. . . . . . . . . . . . My bike has a wire with a . . . . . . . .

Rich, Yours is a 4 valve per cylinder, right? THere are some thing different from the two valve per cylinder 850G... and this (location of sensor) might be one of those.

Other difference might be the type of crankshaft bearings and therfore the general range of oil pressure.

[Nessism]

The so called sensor is just a metal plunger. When there is no oil flow the metal plunger creates a ground path for the oil lamp to illuminate. When oil flows it pushes the plunger off it's seat which disrupts the ground path.
The GS850, like all the other roller bearing crank GS's, has very low oil pressure. The only thing on the bike that really needs pressure is the cam bearing journals. Bottom line, as long as the lamp goes out you are fine.

[Rich82GS750TZ]

Yeah, probably right Dave.

[Redman]

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.Any advice?

Bad connection at the sensor will not make the light come on when it shouldn't. Bad connection at the sensor will keep it from coming on when it should come on (which is why is good to veriry that the light is on before start engine.)

But a short to ground in the instrument cluster can make the light come on when it should not. If the light is on when you think it should not be on, pull the wire off the sensor, that should make the light go off, if it does not go off then ther is a problem in the instrument cluster or somewhere in the wiring.

THe sensor is suppose to make the light come on when the pressure is low , you knew that, but also need to understand that the sesnosor lights the light by effectively connecting the wire to the engine case.

Your description of it used to flicker at idle, then flicker at mid rpm and is now on at mid rpm does sound like a sensor problem or an actaull oil pressure problem. But would be good for you to understand the above also.

[Big T]

The roller bearing motors will run with almost no oil in them - AMHIK
Things to check

Look on the back of the motor from the clutch side - see the wire coming off that white thing- the white thing is the pressure switch and the wire turns the light off. Pull the wire and check its continuity to the oil pressure light. If no problem, then
Remove the switch and check it's not clogged up. It's easier to remove the oval housing that it sits in. Degrease it and clean the electrical connections and reinstall. If the problem persists, then
Get an oil pan gasket, remove the oil and remove the oil pan. Is it all nasty? How about the oil pickup screen?

Report as you go along

[Chuck78]

What he said. Drop the oil pan, and clean the oil pickup filter screen.
Pull the switch out and spray it out with some cleaner. I have had a 2 of these "go bad" and I did not bother cleaning them because I have a stack GS engines floor-to-ceiling on pallet racking to pull spares from...

Cause of the problem could be a faulty petcock as well. Are you experiencing any clutch slipping problems also? If you have gas leaking in on the vacuum line, or if your petcock never fully shuts off, or if your bike is just running way too rich or floats are out of adjustment flooding it, you will be washing down the cylinder walls and leaking gasoline past the piston rings and mixing with the oil, which will thin it considerably and lower your oil pressure, as well as making your clutch friction lining material slip. A full oil change and filter change, perhaps even followed by a second oil change not too many miles later, will help the gasoline problem. After you fix the source of the problem, that is. Pull your spark plugs & visually inspect them to see if they are wet with gasoline and black and sooty.