RGM oil pressure gauge readings

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laurentdom

laurentdom

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Hi All,

I noticed strange readings on my RGM oil pressure gauge during my last ride. The needle was flickering around the 30 psi mark at about 4000 rpms (whereas it usually shows a stable reading of about 40 psi) and pressure was rather declining a bit under acceleration instead of increasing as usual.

The gauge is connected to the LH rocker oil feed. The oil is PENRITE Premium 10-70. The oil pump is new / no oil leaks / no strange engine noise / shows about 60 psi when cold and 10 to 15 idling.

My first suspicion goes to a faulty gauge. Any other idea?

Many thanks for your thoughts.

Laurent
 
I experienced a similar scenario with details, but only once. I use a 20w-50, have a tight big-end clearance and take my mechanical pressure reading off the right front rocker spindle cover.

The readings I saw, similar to yours, began on start-up, but I wasn't shooting oil out of any part of the engine, I was showing readings that swung between 40 and 50 psi, so I motored on to a safe place where I could do a complete visual. I put the motorcycle on its center stand and looked under, over, I pulled the dip stick, checked the filter, but didn't see anything amiss. Still, I have way too much $$ in my engine to ignore such a change so I head to my shop where I can get a better look. I started up and my pressure was back; nice an steady too. Never happened again.

Maybe oil pump cavitation? my engine is a fresh Combat that has had its cases modified to better scavenge, it also has a reed valve breather in place of the conventional breather. No idea why or why I've not seen it again.

There are some real engineers on this forum, perhaps some will weigh-in
 
air bubble in oil pressure gauge line that made it's way up to gauge?
 
Thanks gents.

The scavenge mod has also be made on my crankcase, and I have a Comnoz reed valve breather driving the oil back to the oil tank. The oil tank is ventilated via a 8 mm ID hose and I see no reason why there should be a bottleneck on the Feed or Return lines. But not sure to fully understand what you mean with cavitation.

Re: the air bubble, it could be a reason but why would it occur now, about 2000 miles after the installation of the gauge.

Rgds,

L.
 
Deets55 said:
air bubble in oil pressure gauge line that made it's way up to gauge?
Click to expand...

Air bubble or not, the pressure reading would be the same.
 
Any air in the line would be compressible but the oil can be considered to not be compressible. The rising temperature of the oil/air could show the symptoms you describe. Try bleeding the back of the gauge.
 
I was thinking along the lines of air shocks where the air supplies the spring and oil does the damping. So if the air is in the back of the gauge it would manifest itself as a fluctuating needle. I would expect to see a restrictor in the oil pressure line to damp out fluctuations also.
 
gripper said:
I was thinking along the lines of air shocks where the air supplies the spring and oil does the damping. So if the air is in the back of the gauge it would manifest itself as a fluctuating needle. I would expect to see a restrictor in the oil pressure line to damp out fluctuations also.
Click to expand...

I doubt it would alter the actual pressure reading. I certainly have never bothered to bleed oil gauges.
 
The best thing to do would be to disconnect the gauge & put it in your toolbox. I call them worry gauges. If you know the engine & pump are in good condition, & the oil is top quality, then you have nothing to worry about. The only time you need to use a gauge, is to initially confirm the pressure relief valve is correctly set.
 
L.A.B. said:
Deets55 said:
air bubble in oil pressure gauge line that made it's way up to gauge?
Click to expand...

Air bubble or not, the pressure reading would be the same.
Click to expand...
I was thinking along the lines of air in a hydrolic system. In a brake system you would get a spongy/springy feel. As RPM changes so does oil pressure, thinking along those lines the bubble would act like a little spring till it disapated. This might cause the needle to bounce. Only a suggestion. Nothing difinative. That's why I ended with a question mark not a exclaimton point. :shock:
 
I agree with LAB .... air bubble in line or gauge Bourdon tube will not affect pressure reading.

I also tend to side with Matchless ... oil pressure gauges on a Norton can be sources of anxiety, but I would not go so far to say take it off, (only think twice before putting one on).

Have you checked the pressure relief spring and relief piston for sticking? Any abnormalities at the relief valve will appear at the gauge.

Slick
 
Matchless said:
The best thing to do would be to disconnect the gauge & put it in your toolbox. I call them worry gauges. If you know the engine & pump are in good condition, & the oil is top quality, then you have nothing to worry about. The only time you need to use a gauge, is to initially confirm the pressure relief valve is correctly set.
Click to expand...

Game show buzzer.
not-funny-oil-t24460.html?hilit=Not%20so%20funny
The gage is telling you of an anomoly. Think the gage has flaked out? REPLACE IT. NOW. Guessing/speculating will cost you dearly.
The oil pressure gage was the FIRST item I purchased. $$$$ later, I'd do the same thing.
Cheap as chips by comparison.
 
L.A.B. said:
Deets55 said:
air bubble in oil pressure gauge line that made it's way up to gauge?
Click to expand...

Air bubble or not, the pressure reading would be the same.
Click to expand...
+1
Unlike an automotive brake system (limited VOLUME on hand), air in the OPG line matters not (unlimited volume).
 
concours said:
L.A.B. said:
Deets55 said:
air bubble in oil pressure gauge line that made it's way up to gauge?
Click to expand...

Air bubble or not, the pressure reading would be the same.
Click to expand...
+1
Unlike an automotive brake system (limited VOLUME on hand), air in the OPG line matters not (unlimited volume).
Click to expand...
OK, You guys convinced me. Guess it's not that :oops: :D
 
I might check for a restricted oil lines, both feed from the tank and the return. It seems that the pump, albeit not total, is have a little starvation issue.

Maybe run it up till the gauge show the symptoms and cut the motor immediately the check the oil level in tank.
 
I had a sudden drop in oil pressure from the usual readings and it turned out to be a blown conical seal. If I had considered an oil pressure gauge to be a useless worry inducer I would have ruined an engine. Oil returning to the tank is not an adequate indication that all is well.

Substitute a known good test gauge first.

+3 on an air bubble making no difference, otherwise how would an air pressure gauge work? Seriously, I never bleed gauges. Air is just a compressible fluid and it will transmit the pump pressure just fine.
 
Thanks to you all.

I checked the pressure release device recently. The piston moves freely and I can hear a slight slack between piston and spring as per Mick Hemmings recommendation about spring pre-load.

I changed the conical rubber seal, the oil pump-crankcase paper gasket but not the timing case paper gasket a few weeks ago when I installed the new oil pump.

Maybe useful to double-check but rather unlikely to be involved in the problem IMO.

Comparing with the readings given by another gauge in the same context would be my preferred next step, if I can find another gauge.

L.
 
JimNH said:
I had a sudden drop in oil pressure from the usual readings and it turned out to be a blown conical seal. If I had considered an oil pressure gauge to be a useless worry inducer I would have ruined an engine. Oil returning to the tank is not an adequate indication that all is well.

Substitute a known good test gauge first.

+3 on an air bubble making no difference, otherwise how would an air pressure gauge work? Seriously, I never bleed gauges. Air is just a compressible fluid and it will transmit the pump pressure just fine.
Click to expand...

Yet some insist a fragged crankcase is superior to an OPG as an indicator of oil pressure.
 
[
+3 on an air bubble making no difference, otherwise how would an air pressure gauge work? Seriously, I never bleed gauges. Air is just a compressible fluid and it will transmit the pump pressure just fine.[/quote]



FWIW,

I have air caps on the front forks of my Gold Wing w/ a gauge. It is set @ 5psi static. When I ride I can watch the gauge rise and fall with road bumps. The fork is completely filled with air and partially filled with fluid. If I were to fill the forks completely with fluid it would not compress at all.The same thing applies to gas charged shocks. I understand that air is compressible but at a different rate than fluid, that is why a thought a bubble might cause a gauge to bounce until the system stabilized, especially if it was a non-damped gauge. I have used OPG's w/ clear tubing and seen the void in the fluid and still get a reading on the gauge, but that was on automobiles. Never tried it on a Norton. Apparently the difference between suspension and engine oil pressure might be that one system is closed and the the is open. What ever the case it appears that the general consensus is a bubble would not cause the gauge to fluctuate.

Pete
 
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