Oil pressure

[plumberglen]

How much oil pressure  at idle ?

[kd]

How much oil pressure  at idle ?

Can you help with model, any mods, at what engine and ambient temperature, oil weight, and rpm?

[plumberglen]

2012. 103. 66 degrees Fahrenheit. Fresh rebuild

[kd]

Hot about 20# should be average at 1050 rpm.  Warm, 30 - 35# and Cold could spike to 40 - 50# at start-up.  These would be average and dependent on oil weight (which you didn't say) and pump alignment after rebuild / pump wear.  A little less IMO is not a concern.   Running at highway rpm 30+ hot is average.  Again, depending on the oil weight and actual engine temp.

[plumberglen]

Ok ,start bike cold ,pressure jumps up to 36 -38 psi ,let it warm up ,take for a scoot pressure holds about 32 for a while, then gradually starts to dropdown to 15 or less, then very low on gauge. Engine was just rebuilt, new oil pump, lifters
What do yo think, Sending unit ? gauge? other possibilities?? 

[Coyote]

Really depends on which oil pump. Stock one drops really low at idle. But if the oil light isn't coming on, I'd not worry about it.

[plumberglen]

  Thats what im thinking, Thanks

[JW113]

Mine do the same thing. In fact, on a hot summer day after a ride and the oil is really hot, the oil light will flash at idle, but goes out with just a wee bit of throttle. Perfectly normal.

-JW

[FXDBI]

Did you check the piston oilers when you rebuilt it?    Bob

[Phu Cat]

But if the oil light isn't coming on, I'd not worry about it.

Coyote's right.  Keep in mind the oil pump on Harley's are positive displacement pumps.  If the engine's turning (running) the pump is moving oil even tho your pressure gauge shows little or nothing.

PC

[jmorton10]

Really depends on which oil pump. Stock one drops really low at idle. But if the oil light isn't coming on, I'd not worry about it.

Heck, even if it is coming on it can be completely normal.  A lot of stock bikes will flicker the light on/off at idle on a hot day scaring the sh** out of their owners but there is no problem at all.......

~John

[Hossamania]

How about if sometimes on a cold start the light stays on for a few seconds?
I figure after 125,000 I can live with it. I'm sure the pump is a little worn, o-rings a little brittle, motor just a little tired of my shenanigans.
Surprisingly I haven't seen a flicker at low idle on a hot motor.

[tdrglide]

All my evo motors oil pressure lights flickered at hot idle. None of my twin cam motors have. But I have the TC's idle about 1000-1050rpm. Didn't see what rpm you idle at. I get ~15psi hot idle on current TC motor, ~32-35 anything over 2000

[fbn ent]

Ok ,start bike cold ,pressure jumps up to 36 -38 psi ,let it warm up ,take for a scoot pressure holds about 32 for a while, then gradually starts to dropdown to 15 or less, then very low on gauge. Engine was just rebuilt, new oil pump, lifters
What do yo think, Sending unit ? gauge? other possibilities?? 

Are you saying it drops when riding? That should not be a thing. It was my cam bearings when it happened to me.

[kd]

Ok ,start bike cold ,pressure jumps up to 36 -38 psi ,let it warm up ,take for a scoot pressure holds about 32 for a while, then gradually starts to dropdown to 15 or less, then very low on gauge. Engine was just rebuilt, new oil pump, lifters
What do yo think, Sending unit ? gauge? other possibilities?? 

It's possible the pump wasn't aligned properly when assembled during the rebuild.  A little crank runout will equal some wear and display the symptoms you have.

[Leed]

When my oil sensor started to go it was like that. I never had the light come on even when it dropped to zero. I used a manual gauge and all was good so I replaced the sensor.

[jsachs1]

Anytime I've seen a flicker, mostly after warm up, I put a mechanical gauge to it for an honest oil pressure check. Doesn't take much time at all.
John

[Robb1178]

Just FYI. My newly built 95" zippers BB kit & s&s tc3 oil pump running amsoil 20/50 at highway speeds usually run around 35# hot and 20# @idle. 

[plumberglen]

Ok ,start bike cold ,pressure jumps up to 36 -38 psi ,let it warm up ,take for a scoot pressure holds about 32 for a while, then gradually starts to dropdown to 15 or less, then very low on gauge. Engine was just rebuilt, new oil pump, lifters
What do yo think, Sending unit ? gauge? other possibilities?? 

It's possible the pump wasn't aligned properly when assembled during the rebuild.  A little crank runout will equal some wear and display the symptoms you have.

that was the issue , bolts on pump were loose

[bigfoot5x]

I know that oil pressure at idle gets pretty low on the older models. I've never had a flickering lights on our bikes and that would concern me. It's better on the newer ones. One thing I had to convince myself was that oil pressure isn't quite as critical on a Harley because of the design of the engine. On the old small block Chevy it was expected to have 10 psi per 1000 rpm to keep the crank and cam bearings lubed. On car engines, the spinning parts actually ride on the film of oil so the 2 metals do not touch. On a Harley most everything is spinning in some type of roller bearings. They need oil in them but not like a car's bearings need oil.

[JSD]

I know that oil pressure at idle gets pretty low on the older models. I've never had a flickering lights on our bikes and that would concern me. It's better on the newer ones. One thing I had to convince myself was that oil pressure isn't quite as critical on a Harley because of the design of the engine. On the old small block Chevy it was expected to have 10 psi per 1000 rpm to keep the crank and cam bearings lubed. On car engines, the spinning parts actually ride on the film of oil so the 2 metals do not touch. On a Harley most everything is spinning in some type of roller bearings. They need oil in them but not like a car's bearings need oil.

What about the later cam plates they have cam and pinion running on the plate not even bronze bush. They need oil pressure in my opinion.

[Ohio HD]

What about the later cam plates they have cam and pinion running on the plate not even bronze bush. They need oil pressure in my opinion.

The cams and the pinion shaft in the cam plate don't ride on a cushion of oil. As long as there's oil flow to the cam plate bores they're fine. And they get that oil right from the pump about an inch from them.

If you think about it, the spec on the pinion shaft run out is a maximum of 0.012". No way the shaft can ride on a cushion of oil.

[JSD]

. 012" allowed max Shame on the MCO. 

[cheech]

What about the later cam plates they have cam and pinion running on the plate not even bronze bush. They need oil pressure in my opinion.

The cams and the pinion shaft in the cam plate don't ride on a cushion of oil. As long as there's oil flow to the cam plate bores they're fine. And they get that oil right from the pump about an inch from them.

If you think about it, the spec on the pinion shaft run out is a maximum of 0.012". No way the shaft can ride on a cushion of oil.

I might be reading this the wrong way.

Exclude the pinion shaft because it's a "rigid" (not necessarily in Harleys LOL) part of the crank.
So I'm with you on that.

He never mentioned a cushion of oil but did say

They need oil pressure in my opinion.

Which the cams in the later Twincams do need oil pressure and you allude to by saying "they get flow from the pump"
As they are true hydrodynamic bearings. (At least I believe them to be)
No bushing as he said nor rolling element bearings.
Just the cam journals and the aluminum bore of the cam plate.

So the cams are riding on a fluid film.

Someone may refer to that as a "cushion of oil" I don't know.

So you saying

The cams and the pinion shaft in the cam plate don't ride on a cushion of oil.

Are you disagreeing with him in them needing pressure?

Or do you not consider them hydrodynamic bearings?

[Ohio HD]

Of course there is always oil pressure, otherwise there is no flow of oil through the oil passages. The cams will ride on a lubricated parent material of the cam plate or on a bushing in some earlier TC cam plates. There is of course oil to keep the cams from seizing and to cool the cams and cam plate as they cams spin in the cam plate. This occurs if you have three PSI showing at the oil pressure port or thirty PSI. My meaning was you don't need to have much pressure at an idle. As long as oil flows to the cams and pinion they're lubricated in the cam plate.