can there be any problem with cold oil running 60-65 lbs, and pegging the gauge with revs? I'm taking it easy for about 5 miles until it settles down to a nice 50 lbs cruise pressure, because I am worried about blowing out the Amsoil filter, running 20/50 Mobil1 Vtwin with an almost stock 88, just Andrews 21's for torque, fairly open but regulated pipes, and a K&N filter . I'll be towing a loaded trailer and the wife t his weekend and worry a bit.

 

My local favourite indy calls oil gauges 'worry' gauges. I don't have one on any of my Harleys, so just pretend you don't have one on yours! High pressure on a cold engine is normal, so I don't think you have anything to worry about.

 

40psi is more normal for cold oil on startup and 30-35psi is more normal for cruise at operating temperature for a stock TC88. Is this a recent development? What was the last thing you did before experiencing higher than normal oil pressure? Are you running OEM filter? The problem could be a bad guage or bad sending unit. First thing to do would be to hook up a gauge directly to the engine and see what reading you get. If normal, then you know the sending unit or gauge is the offender.

However, if the oil pressure is truly that high, something's not right. Without getting into the weeds, the TC oiling system is a low pressure system designed to supply volume and it is pretty low tech but more than adequate to keep the TC engine alive and well for a long time.

Normal oil pressure should be about 5-8psi at idle and about 35psi at cruise; give or take. Higher than normal oil pressures can do more harm than good; the main problem being aeration of the oil, or entrainment of air in the oil. Air entrainment is not good.

If the pressures are truly that high, the oil pressure releif valve in the cam plate could be sticking causing a restriction. Pretty simple thing to address by removing the sring and valve, cleaning up the valve, i.e., smooth it up a bit with some fine emery cloth and reinstall.

 

sorry guys, just re-read my post and I had omitted that I've put in a spring tension pin on the oil relief valve, causing the high pressures. It's just that the pressure went far above what I expected.
I read that it's not uncommon for the Twins to drop off oil pressure as they age (32k on mine) and zero at idle hot was buggin' me. Hot idle pressures are back up to about 8 now, and cruise at 50. I cruise fast.

 

You don't need that kind of pressure, pull the spring.

 

If you are experience 65lbs oil pressure the oil filter will go into by-pass and unfiltered oil will be circulating through the engine. Iirc Harley tc oil filters have a 60lbs by-pass.
That is actually the reason it's so important to have an oil filter that is built to Harleys specs and not an automotive filter,the by-pass spec.
The by-pass spec is that high because of the 20w-50 we use in the engines. On a cold morning the oil is so thick that it's harder to pump which equals more pressure.

 

Not quite right.

If the oil pump exceeds +/-35psi, a bypass valve in the cam plate will begin to open and route some of the oil back to the scavenge side of the pump. This bypassed oil will not circulate through the engine nor will it reach the filter. This is to limit the maximum pressure of the oil pump. That's the reason I previously suggested that the cam plate bypass valve could be sticking.

During normal operation the oil pump in one of these bikes will operate at 20-30 PSI.The filter also has a bypass valve which will open when the pressure difference across the media reaches 8psi. This can happen if the filter gets very dirty, if the oil is too thick, from being very cold etc, and it may do it briefly when the RPM of the engine gets real high under rapid acceleration but normally all the oil is being filtered. Many are confused on the 8psi required to open the oil filter bypass and think it is an inlet pressure when it is a pressure difference across the media. A bypass that opened under 8psi inlet pressure would pretty much eliminate the need for a filter.

Quadancer needs to remove the spring; it is not doing anything good for the engine and has the potential do to bad.

 

Really? I have a stock 120r that does this very thing.... ALL the 11 and 12 120Rs do this. So my filters, etc are now no good all of a sudden?

60 cold, 50+ hot. 30s hot idle

 

The previous was posted in the general context of a stock TC88. Different oil pump and I have not run across one that ran oil pressures as high as the OP is experiencing. Since I have no experience with the 120R, I can't respond in that regard. How did you come to the conclusion that filters are no good from my previous post? Was not said or implied?

 

On my 88" I have the stock pump and plate, also using an aftermarket by-pass spring and also have increased oil pressure. Pins the gauge when cold, somewhere over 40 psi when warm and cruising and drops in between 30 and 0 when warm and idling. Very happy with the way it works. Less top end/valve train noise, running Andrews 26's with stock lifters and p-rods.
To the original poster, just run it. Until the no oil pressure light comes on or it starts making some un-god-ly noises, keep your eyes on the road and have a nice ride!!