Another oil pressure puzzle

1979 Kz1000 ride it a few mile shut it off start it back uo 5 to 10 mins. later oil light is on and stays on until you get up to speed then goes out.Light never comes on while running hiway speed or heavy threashing .bike has Lockhart cooler with 1/2 inch lines have changed pressure switch with no change.doesnt do this after sitting for more than 30 mins. or so.just if you let ut sit 5 to 10 mins. any ideas.(also shows no oil pressure on gauge when this happens). Thanks

Ok i got a theory on this want to get a second opinion this bike has a yoshimura header and it is right against the oil foliter bolt could this be super heating the oil going to the idiot light switch causing a low pressure reading?

76 LTD wrote:

1979 Kz1000 ride it a few mile shut it off start it back uo 5 to 10 mins. later oil light is on and stays on until you get up to speed then goes out.Light never comes on while running hiway speed or heavy threashing .bike has Lockhart cooler with 1/2 inch lines have changed pressure switch with no change.doesnt do this after sitting for more than 30 mins. or so.just if you let ut sit 5 to 10 mins. any ideas.(also shows no oil pressure on gauge when this happens)...
...got a theory on this want to get a second opinion this bike has a yoshimura header and it is right against the oil foliter bolt could this be super heating the oil going to the idiot light switch causing a low pressure reading?

Some random thoughts ---

Am presupposing good unclogged oil filter with fresh oil at correct level and proper viscosity, with both filter by-pass and crankcase vent up to specs.

Thinking both oil pressure light and gauge read pressure immediately from the oil filter, so if theoretically super-heated oil fails to activate the light, it must also be failing to activate the gauge. Could of course test the super-heated oil theory by experimenting with a different exhaust system. But am wondering if there's enough slack available (with hanger bracket loosened?) to press a thin wooden shim between the header and filter bolt to temporarily insulate the parts while re-testing.

Following your theory, am wondering if the oil pump itself may be contorting from the excessive heat.

Will be interesting to learn the ultimate resolution.

when did the problem start? after an oil filter change? is it possible that you put the spring on the wrong side of the filter pushing the filter away from the engine and letting hot oil blow past the rubber seal in the filter?,, this happened to me once but from a mechanic

After more pondering about the overheating theory, am thinking the contact between header and filter bolt is super-heating not only the filter area but transferring heat from the header via the filter bolt to the entire oil pan.

Think "deep fat fryer" analogy, especially just after engine shut off, with oil no longer circulating and toasty-hot header likened to the burner on a kitchen range heating up a "pan" of oil.

If not already done, might consider using an oil temperature guage to measure operating temperature during normal highway cruising. Am guessing the oil temperature will be above ideal, due to additional heat input from the exhaust header being in direct contact with the filter bolt.

Believing some clearance (maybe 1/4 inch?) between header and filter bolt could resolve the problem (and validate your theory).

Am reasonably certain the Yoshimura exhaust system is not designed for fitment in direct contact with any under-engine part. Would a longer exhaust hanger bracket be feasible?

IMO the Yoshimura exhaust system is beautiful, performs exceedingly well, and tucks in very nicely. The only reason I replaced mine was because of having to remove it for an oil change.

Already checked or replaced all the things mentioned oil gets changed every 1500 miles whether it needs it or not.im gonna put the kerker back on and see if makes a difference if so i will buy a low pro filter cover and bolt from APE to get the clearance needed for the yoshi.This is a low miles one owner bike that has always had meticulous care so im sure its not a machanical problem.

Any chance this condition has existed ever since the oil cooler was added?

KZCSI

Listen to KZCSI, 76 LTD.

Science (physics, actually) will set you free.

There are many similarities between electricity and hydraulics, including the power triangle and the math (boo, hiss).

Voltage = Current x Resistance
Psi = gpH x Resistance

Fluid Pressure is equal to flow x resistance to flow.

Fluid pressure is a byproduct of flow and resistance created within the circuit.

Flow is the amount of fluid passing through the circuit.

Resistance is created by the orifices within the circuit.

"Lockhart cooler with 1/2 inch lines"

By installing your cooler, you've created a low resistance in parallel with your traditional oil routes, lowering your overall circuit resistance. Hence the drop in oil pressure.

Without Cooler

Psi = gpH x Resistance

40 = 3.3 x 12

With Cooler

29.7 = 3.3 x 9

The numbers are imaginary, but get the point across. Assume idle.

"never comes on while running hiway speed or heavy threashing"

The pump will put out more flow when engine is turning more RPM

36 = 4 x 9


There is an easy way to prove it, put a couple of caps on the lines and give it a go.

If you wish to retain the oil cooler, put a flow restrictor in your oil cooler circuit to increase overall circuit resistance.

Rob.