Oil Pressure Gauge

Okay this is a long winded way to ask a simple question (namely what should I be reading on my oil pressure gauge?).

Background:

I own an 850 Mk III that has had a problem with wet sumping for some time. It will completely drain the oil tank in about 5 days... I'm in the military and am frequently gone for a few weeks (or months) at a time, and got sick of draining out the sump every time this happend... also blew a crank seal at one point, and oil was flooding the primary regularly with every wet sump (possible the seal was installed incorrectly though... restoration was conducted at a rather disreputable shop and there have been all sorts of problems).

Anyhow, after tearing my hair out (and installing a new crank seal), I finally decided to bite the bullet and install a Miles type anti-wet sump valve from our good friends at CNW. Purchased an oil pressure gauge from our friends at Old Britts to go along with it to allow me to keep an eye on things.

Everything is installed and up and running. Install went fairly well, except that when I tightened the banjo on at the base of the pressure gauge the gauge rotated some 90 degrees. Pulled it out to inspect the little black pressure relief seal and everything looks good. Reinstalled... reused the crush washers and now a very small leak there (drop forms and falls about every 5 minutes I would guess), but no big deal I have a few spares lying around and will fix before the next ride.

Took it out for a test run. The gauge reads off a line coming from the left rocker feed (it's actually a pretty clever little setup)... After the bike warms up I get about 10 lbs at 4000 rpm, 5 lbs at 3000 rpm, and pretty much no reading on the gauge below that. The gauge reads off a line coming from the left rocker feed (it's actually a pretty clever little setup). I'm guessing this reading is *way* low. Keep in mind the Miles anti-sump valve is installed, which isn't helping things I'm sure but the boys at CNW say that should only drop pressure 10% or less. Looking into the tank the oil return is strong, even at idle. Running 20w50 Castrol GTX. I ensured the oil line was primed upstream and downstream of the Miles valve and checked that return was coming back to the oil tank.

Wondering what people's thoughts are on this. I'm not sure how accurate that gauge is. If it is correct, then it appears I have a serious oil pump issue to deal with. At this point I'm thinking maybe I should send it off to AMR to have them overhaul it and install the check ball upgrade at the outlet, allowing me to possibly eliminate the Miles valve.

Cheers,

- HJ

O.K., so now, take the anti-sump valve out and see what you have for pressure at idle.

I had been running an oil pressure gauge before I installed a valve of the same type. After I installed the check valve my OP went to zero at idle with hot oil. Prior to using the valve I would have about 5 PSI at idle with hot oil. Cold oil should give you at least 10 PSI at idle. Startup OP is usually much higher for a short time.

Although many of those check valves are in use, I'm not a fan of them. They are a blockage in the feed line to the pump which must be overcome with enough vacuum from the pump to unload the spring pressure holding the valve closed. If the pump should lose it's prime, you'll be running with no oil pressure, but not for long. IMO, the correct way to address oil sumping is to install a spring loaded ball at the output of the pump. Also, the pump shafts need to be sealed with "O" rings. AMR provides this service for a not too great of sum. Never again will I ever put anything between the oil tank and oil pump except an oil line.

I'm certain there will be responses to the contrary of mine. I'm stating my experience with the anti-sump check valve. This was with a fresh rebuild, crank journals turned, new shells and a new oil pump.

How many miles on the bike? Worn rod bearings can exhibit low oil pressure. I've been told by experts the oil pumps themselves are often worn/poorly fit. Search and read. Here, this will prime the pump: pump-flow-t11217-15.html

I don't have any real answers here, but a couple of ideas. I would be tempted to remove the line from the back of the pressure gauge and start up the bike to see how much oil I was really getting out of that line. I have done this at the left rocker and the flow is pretty positive. I don't have a measurement. I had taken a latex glove and rubber banded it over the end and it filled it rapidly. This may not tell you if the gauge is good but at least if there is very little flow you know you need to look at the pump, valve or restrictions in the lines.

I committed the ultimate sin and installed a small ball valve on the oil line. I only close it when the bike will sit for long periods. If you are worried that you will forget it, then hang your keys on it, or don't install it at all as many would suggest.

The other thing you might be experiencing is a oil pressure relief valve that is set too low or stuck partly open. It might be worth pulling it off and giving it a cleaning and checking to see that it is properly set up.

Russ

The OPRV will only dump off oil above a preset pressure. It will not decrease or increase pump output.

I'll suggest putting straight VR-1 SAE50 in it and see what readings you get then. Can't hurt anything.

Dave
69S

JimC said:

The OPRV will only dump off oil above a preset pressure. It will not decrease or increase pump output.

Click to expand...

Wouldn't it dump off excess pressure if it had a faulty spring or the piston stuck in the open position? I thought it might.

as you have MK3 you already have an anti sump valve in the timing cover BUT it is the piston type. these are well known to stick which when that happens you might as well not have it. you said that it will wet sump in a week so THAT is a VERY good indication that the oil pump is pretty much JUNK with very large clearances in places that just tightening the end clearance WILL NOT fix. as to the low oil pressure you need to try a second gauge to compare readings to what could be a damaged gauge from it turning in it's housing. also as dave said try the straight 50 WT oil as a test. IMHO you will be buying a new oil pump before long.

as you have MK3 you already have an anti sump valve in the timing cover

Click to expand...

That was an important point and I missed it.

My comment about inline anti-sump valves still stands.

When HJ installed the valve, he installed the oil pressure gauge, too. Never knowing what his OP indications were prior to the valve installation. My thinking was to remove the valve to see if there was any difference in OP.

Low pressure at the rockers is about the norm, the crank/shell clearance will be venting off the pressure,like nobodies business when the oil is hot.
Oil grade as dogT says will produce a differant reading on the gauge, chuck in some straight 50, if you want to see more on the gauge.

Don't the cam lobes/lifters get lubrication from pushrod tunnels? If that's so, I'd like to see something other than zero oil pressure at idle from the rocker shaft.

Jim, How did the early 650ss get it's rocker oil. ? It was just a pipe connected to the return, If the pipe was disconnected and held higher than the oil tank, it stopped flowing...well should i say dribbling!
As you say the rocker spindle holes control the oil to the head,after a while it drip's down the push rod tunnel,hopefully getting onto the cam face :!:
Engine lube on a commando scores 6/10.
Back in the 1950's did norton,Triumph or Bsa really care about engine long liverty?

I have a similar experience with my 74 850. It's got the CNW breather kit installed and I also installed the Old Britts oil gauge. Reads pretty close to 70 psi upon start up, both for idle and running out at 2 - 3K RPM. In a few minutes the idle pressure starts to drop but in the 2 - 3K range is still up at 70. After about 10 minutes of running at 3k - 4k, the pressure is below 60, after 20 minutes of running at the same speed the pressure is down to 40 psi. After 30 minutes of running, the pressure is around 20 psi at 3K, 25 psi at 4K, and just barely registers off the gauge stop at idle.

I used an infrared temp sensor to check the oil temp in the tank after running for 20 minutes and it was right at 200F. After 30 minutes when the pressure had stabilized, the oil temp in the tank is 234F. All the reading for temp and pressure are taken on days that are right at 100F ambient temp.

I'm using HD Big Twin petroleum 20-50, but will change to Royal Purple 20 50 when the new rings are fully seated. Royal Purple Syn is supposed to reduce oil temp by reducing friction, but I'll be able to check that. I've also considered going to straight 50 wt, which is probably not a bad idea for the Texas summers.

When I first installed the oil pressure gauge, I was alarmed about how much the pressure dropped and took out the CNW check valve I was running. There's no difference in oil pressure or pressure drop with or without the check valve in place.

Oh, and the bike will drain all oil into the sump if it sits more than a week (without check valve).

If' I don't see much of a change with the Royal Purple or straight 50W, I'll probably pull the oil pump and lap the body to tighten up the clearances.

I'm not familiar with the 650SS, but I agree that the Atlas/Commando lubrication system leaves a lot to be desired. I haven't dug into any of the newer high performance motorcycle engines, but I would imagine they have a much better lubrication system than the Norton.

JimC said:

The OPRV will only dump off oil above a preset pressure. It will not decrease or increase pump output.

Click to expand...

If the pressure regulator or relief valve stays open or jams open EG broken spring does this not give a open path back to the low pressure side hence drop off both flow then also pressure ??? :?:

Norton Dave said:

JimC said:

The OPRV will only dump off oil above a preset pressure. It will not decrease or increase pump output.

Click to expand...

If the pressure regulator or relief valve stays open or jams open EG broken spring does this not give a open path back to the low pressure side hence drop off both flow then also pressure ??? :?:

Click to expand...

No doubt it will. My point was the OPRV will not affect the output of the oil pump. It's still going to pump out the same volume, regardless what the OPRV is doing. I've seen posts here that say they are trying to increase low oil pressure by adding shims to the OPRV. If the pump is not putting out enough oil, the pressure will be too low. You could plug the oil relief hole and the OP would not increase with a weak pump. The Norton's oil pressure seems to be greatly affected by temperature of the oil.

I've never experienced a stuck open OPRV, but I have had one that was stuck closed. The oil pressure at startup is frightening. IIRC, it was somewhere around 200 psi.

Pressure is not important, it's flow rate and how conponents get a good and quick supply, a Cam and followers running in a oil bath will last a life time..with Zero pressure, a dribble from the head down the push rod tunnel,after several minutes from starting ..well thats another story!
Oil pressure is a measure of ressistance , a consant 100psi means nothing in a Norton engine..infact low pressure is better..it means the pump is producing a good flow..the higher the pressure..less flow! lower ..well oil is on the move...Hope this make's sence.

mgrant said:

I have a similar experience with my 74 850. It's got the CNW breather kit installed and I also installed the Old Britts oil gauge. Reads pretty close to 70 psi upon start up, both for idle and running out at 2 - 3K RPM. In a few minutes the idle pressure starts to drop but in the 2 - 3K range is still up at 70. After about 10 minutes of running at 3k - 4k, the pressure is below 60, after 20 minutes of running at the same speed the pressure is down to 40 psi. After 30 minutes of running, the pressure is around 20 psi at 3K, 25 psi at 4K, and just barely registers off the gauge stop at idle.

I used an infrared temp sensor to check the oil temp in the tank after running for 20 minutes and it was right at 200F. After 30 minutes when the pressure had stabilized, the oil temp in the tank is 234F. All the reading for temp and pressure are taken on days that are right at 100F ambient temp.

I'm using HD Big Twin petroleum 20-50, but will change to Royal Purple 20 50 when the new rings are fully seated. Royal Purple Syn is supposed to reduce oil temp by reducing friction, but I'll be able to check that. I've also considered going to straight 50 wt, which is probably not a bad idea for the Texas summers.

When I first installed the oil pressure gauge, I was alarmed about how much the pressure dropped and took out the CNW check valve I was running. There's no difference in oil pressure or pressure drop with or without the check valve in place.

Oh, and the bike will drain all oil into the sump if it sits more than a week (without check valve).

If' I don't see much of a change with the Royal Purple or straight 50W, I'll probably pull the oil pump and lap the body to tighten up the clearances.

Click to expand...

Oil pressure is a measure of ressistance

Click to expand...

Measured oil pressure is a function of flow volume and resistance to flow. If oil pressure decreases, one or both of the other factors have changed. In most engines, if the pressure rapidly decreases it's probably an indication the flow decreased, given there is no change in resistance such as a line blowing. In the case where clearances, such as rod bearing clearance opening up, the lower pressure will indicate a decrease in resistance, not flow. As John implies, an abnormally high oil pressure could mean the oil is not flowing as well as it should, such as a blockage. Whereas, a broken oil line would lower pressure, but not flow from the pump. Of course, the critical components would not be getting oil if they were aft of the broken line.

I am not trying to argumentative, I am just really dense. If a pressure relief valve is stuck closed and it raises the oil pressure at start up, then why wouldn't one that was stuck open see low oil pressure after warm up? Wouldn't it essentially be the same effect as worn crank bearings allowing oil to flow more freely?

Sometimes the easiest stuff just completely eludes me.

Russ

Anyone know how to measure the relief pressure of the OPRV with it out of the engine or is it hit or miss?
Regards Mike