Losing oil pressure

[Hauula Pan]

My 1952 FL with original oil pump fires up cold with approx. 32-psi and my light goes right out. As the engine heats up the pressure drops & the light comes on. After about 5 miles I have to keep increasing the rpm to keep the light out & after about 10 miles the gauge has pretty much dropped to 0-psi and the light will not go out at all. I've also noticed that when its cold there is no oil leakage around the pump but after I ride about 5 to 10 miles I get some drops on the ground from the pump when I stop & turn it off. Any ideas why I've got great pressure cold & none once its warmed up? The pump body was chromed several years ago & I had it re-chromed last year when I did a rebuild. I'm wondering if its possible that the pump face is not perfectly flat now and as the engine heats up & the oil thins out if I'm maybe sucking air ? I have also turned the pressure adj. in from the initial setting of 3/8" & this raised the initial cold pressure up a couple of lbs. & allowed me to go a bit further before the pressure drops & the light comes on but it does not solve the problem, it just takes a little longer for the pressure to drop. I do not understand why I can have such great pressure to begin with & have it drop to 0 when the engine heats up. Appreciate any ideas here.

[JR JOHNSON]

HI, MY QUESTION FOR ME TO ASK ,DID YOU HAVE A OIL PRESURE PROBS BEFORE YOU REBUILT YOUR PAN, WAS THIS A MAJOR OVERHAUL,OUT OF FRAME? MY 50 HAD ABOUT 5 LBS GOING DOWN THE ROAD,LOTS OF OIL RETURING TO TANK,NOTHING AT IDLE,BUT I HAD OIL GOING TO THE TANK. CHROMING THE PUMP,LONG AS THEY SEALED UP,NOT DOING THE FACES OF THE PUMP SHOULD BE OK,BUT BEWARE, YOU PROBLEY GET BEAT UP BY PEOPLE FROM THIS SITE SAYING CHROME WON'T GET YA HOME THING. IF YOU COULD LETS US KNOW IF THIS JUST HAPPEN,OR AFTER YOUR REBUILD. I'M PROBLEY NOT MUCH HELP,BUT I'LL TRY WITH RESPECT JR

[NightShift]

Dear Hauula Pan,
Lets understand right off that the more the flow is shut down by the oil being cold and syrupy the more pressure shows on the gauge.

That means that the lower the pressure gets with heat the more oil gets through because the oil gets thinner and easier to pump.

So a gauge only tells you if you are warmed up!

And you need a pressure switch that only needs four of five pounds to to turn off the light.

The chrome thing is a whole another scary can of worms,

[Hog54]

The number one thing to ask is what is the temperature where you are.My light will come on at every stoplight if its over 80 degrees.And as long as you see it going back in the oil tank its fine.I just noticed that your in california.Isnt it like 100 degrees there right now?My light would never go out if it was 100 degrees here.lol

[Bosheff]

A very, very large percentage of the pans out there do just exactly what yer's is doin'. As long as the oil is returnin' to the tank you're probably gonna be O.K....bosheff

[Hauula Pan]

I don't know what it was doing before the rebuild as I never had a light or gauge or anything before. I know it is normal for the pressure to drop to about 4 psi. & sometimes even 2 psi if the weather is hot, but I'm dropping to 0. I do have oil returning to the tank, although it has a lot of air & sputters a lot. I know its probably just oil mixed with scavenged air but I'm just not sure if I'm getting enough oil to the top end. Since its leaking I've decided to go ahead & pull the pump & rebuild it just to be safe. I ordered new gears, and a rebuild kit with new springs, balls & gaskets & once its off I'll re-check the faces & mill them if they're not perfectly flat. I figure its a lot cheaper to rebuild the pump than the engine. ( I've heard that years ago guys used to change out the drive gears inside the timing case with a set that would turn the pump faster but no one I've talked to knows where they got them. Has anyone heard of doing this?) Any way I'll check back & let ya know if rebuilding the pump fixes my issue. Thanks for the replies. I've been following this site for a little over a year now, it is a fantastic site and everyone on it is so helpful, I could not have gotten my bike back to stock without all the help I've received from the folks here, and the few times I had an answer for someone else I've done my best to reply to them. My thanks again to everyone. Lets keep the old iron on the road.

[steinauge]

Your original pump drive gear set has 5 teeth on the drive and 25 on the driven.73 and later models had 6-24.If you want a 6-24 gearset for your splined pinion shaft S&S sells them.If your gear protrusion in your pump is OK and as Bosheff says you have oil return chances are that all is well.If you really are drying out the rockers when it is hot it will start to squeak(seriously).Best thing to do is take the gauge off and like Shifty said get a sending unit that goes off at 5 lbs.If it was mine I would verify hot oil return and disconnect the sending unit. IMO chroming oil pumps is a very bad idea! When they chrome the pump the body gets buffed-likely so do the gasket surfaces.

[Panshovevo]

I've read a number of oil pressure related posts over the last couple of months, and have been thinking all along that it would be good to know how accurate the gauges and pressure switches are. When I worked at an aircraft engine Certified Repair Staion, we had a suitcase sized device for testing turbocharger controls, wastegates, etc. It had calibrated low pressure gauges, and a manually operated air pump to provide pressure for testing. It might be worth a call to a local aircraft repair facility to see if they have this type of tester, and find out if they could and would check the gauge and pressure switch for you.
Anyone have any other ideas for low pressure calibration equipment that would do the job? Something in the 0-10 psi range?
Regards,
John

Edited to add that all gauges and pressure switches are NOT created equal (and rarely read the same).