Oil Pressure light is on !!!!

I need wise help here.

I have finished my bike FINALLY! THANK GOD!

but yesterday i rode the bike about a mile to the gas station. On my way back, my oil pressure light kicked on. I called my mechanic today he suggested either the switch is bad (switch, or wiring), or the filter (to the pump? not the main oil filter) is clogged thanks to the water foam that we've been slowly working out of the block.

He suggests testing the switch with an external light. How do i go about doing this!?

1. No oil pressure
2. Bad switch
3. Pinched or frayed wire grounding out. This happened to me. Wire got pinched when installing starter cover.

I agree ! ... but how do i go about testing the wire? i know that is what i should test first?

use a external testing light? let it run sitting still for a while?

If you have a multimeter, set it on OHMs(looks like an upside down horseshoe)or on some meters,resistance.Place it in the lowest ohm setting,disconnect the bullet connector on the oil pressure switch from the wiring harness, and then put the RED probe where the switch connector went, and the BLACK probe on a good frame ground(or the Negative battery terminal.

If there's short(pinched wire,frayed insulation) the meter will indicate with a full needle delection if Analog, and possibly a sound if Digital. Also check the switch too, as they can fail internally

The switch is the ground wire for the oil light. One side of the oil light has a constant 12V going to it. The other wire goes to the switch which is grounded to the engine. When the you first turn on the ignition the electrical circuit is completed so the light comes on. When the engine is started the oil pressure opens the electrical circuit which then turns the light off.
To test the wire with a light you must use the wire from the switch as the ground wire. The easiest method is to disconnect the wire from the switch and ground it to the engine. Your oil light should come on, then unground the wire and the light should turn off. Testing the switch itself is a little more involved. If the wire test is good then I would swap out the sending unit with a known good one.

mcmelend wrote: but yesterday i rode the bike about a mile to the gas station. On my way back, my oil pressure light kicked on. I called my mechanic today he suggested either the switch is bad (switch, or wiring), or the filter (to the pump? not the main oil filter) is clogged thanks to the water foam that we've been slowly working out of the block.

He suggests testing the switch with an external light. How do i go about doing this!?

The timing of the oil light coming on is telling -- here's one way to get some confidence that the wiring or the switch is *not* the cause of the problem:

1) park the bike for a while, let it cool down completely

2) turn the ignition on but don't start the engine

3) is the oil light on? If 'yes' that's a good sign

4) now start the motor -- does the oil light go out? If 'yes' that's a good sign

5) shut the motor off immediately.

6) repeat steps 1 through 5 to give you confidence that the oil light, switch and wiring are okay.


Sounds like a blockage to me if the above steps show the oil light behaving normally.

The telling part was that the oil light behaves normally until you're running for awhile.

I have had 2 occasions when my oil pressure light came on. To make a long story short I disconnected the wire from the sending unit (behind the points cover on my bike) cleaned around the top of the sending unit with a wipe and re connected. Wallah ! Fixed.

In both cases I think the wire was shorting due to dirt or moisture.
Hope your fix is as simple
Good luck

I have a random thought / question.

if it is an actual oil problem, why would it not kick the sensor right away when running the motor? why does it wait till after a mile to kick?

a thought, maybe the wire is pinched, and when the motor warms (metal expands) it presses the pinch and grounds thus tripping the light?


keep the thoughts comin !

mcmelend wrote: I have a random thought / question.

if it is an actual oil problem, why would it not kick the sensor right away when running the motor? why does it wait till after a mile to kick?

a thought, maybe the wire is pinched, and when the motor warms (metal expands) it presses the pinch and grounds thus tripping the light?


keep the thoughts comin !

Easy way to test that. The engine gets hot when you're riding, no question -- but keep one thing in mind -- it's an air cooled motor. So unless you were sitting at a lot of long stop lights during that ride, if you think about it, the engine temp was being kept down by the air cooling.


If the heat of the engine is causing metal to expand and intermittently disrupt the connection (open or short) to the oil switch, an easy way to check:


1) speed up the engine heating process -- since it took apparently a few minutes of riding and being cooled by the air.......

2) start the motor and let it run on the stand, ie. remove the air cooling.


The engine will get real hot real fast with no air cooling. One way to guestimate this is:

A) how many minutes of running and driving on the road and being cooled by the flowing air did it take for the oil light to come on?

knowing the answer to (A), you know with certainty that if engine heat is causing the problem, you can run the engine with the bike on the stand, ie. not moving, for less than the time in (A).

Could be a marginal blockage in one of the oil passages, or an intermittently working oil pump, or a blocked intake screen on the oil pump (drop the oil pan to check).

If it is in fact an oil pump problem it could be that the light comes on after the oil gets hot and thins down a bit. Ed

I will try all the above once i get off work. I'm going to first look for a messed up wire possible? then i'll proceed to start the motor and let it run till it's hot and if the light kicks. If it does, then i'm not going to mess with it. Don't have the time, i'll let the pro determine if it is my pump or not...

650ed wrote: If it is in fact an oil pump problem it could be that the light comes on after the oil gets hot and thins down a bit. Ed

Yep. That would worry me enough to buy or rent an oil pressure gauuge to isntall at the hole where the sender is. I have one I bought way back when.

That part:

he suggested either the switch is bad (switch, or wiring), or the filter (to the pump? not the main oil filter) is clogged thanks to the water foam that we've been slowly working out of the block

would really scare me. I would have risned the water out with solvent and blown it clean. Water and oil don't mix... literally.