Oil Pressure Gauge

Reggie · Jul 9, 2012

Hi, I get similar readings, to mgrant.
Basically at start up 70 psi (Imust take a look at the o/p/r valve sometime).
Suffice to say, when properly warmed up, I get approx 10 to maybe near15 psi per 1,000 rpm. e.g. at 3000rpm 30 to 45 psi.
The only time mine drops below 10 psi per 1000 rpm is when I am riding very hard such as sustained cruising at over 70mph or faster, then it can drop below this 10 per thousand rpm figure, basically because the oil is getting so hot I assume it becomes less viscous.
I run 20/50 weight oil and have the same Oldbritts gauge as you, taken from the left rocker feed. Here the oil is under feed pressure.

A friend of mine once had a low oil pressure reading, even though the oil was returning plentyfully to the oil tank. The cause of the low pressure was the oil seal in the timing case cover which fits over the right side crankshaft. It had blown (turned inside out). If this isn't the cause I would do a trial without the non return valve to see if and what the difference is.

Hobot · Jul 9, 2012

Brit bikes originated in chilly climate and loose clearance technology so the relief valve was to prevent over pressure till warmed. The oil pressure gauge will show the relief threshold pressure, if the oil is thick-cold enough to cause ti to open and recirculate excess pressure. That is: the OPRV does not influence normal hot run pressures. Norton don't need to show any pressure at hwy speed. Norton dropped the oil guage option in a about a season after the horrified reports flooded in. Optimally 10 PSI/1000 rpm is great to shoot for but crank sling is enough to protect the bottom end unless maybe all out racing extreme and head only needs a squirt now and then, but to keep valve springs cooler. Ideally keep upping the viscosity till PSI needle position calms thou nerves.

Comos told me when he rifle drilled his cam shaft he put a .17" restrictor in fed and that was enough to drop PSI to zero running so of course he just made himself a bigger pump to get pressure back.

JimC · Jul 9, 2012

rvich said:
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

To answer your question: Yes, it would seem so.

No, you are not dense. You may have found the problem. Hungry Joe stated he was reading about 10 psi @ 4000 rpm. This is too low. I believe that the rule-of-thumb is 10 psi for every 1000 rpm. I do know when the oil gets really hot, hard freeway run with the temperature being 80º+, I can't quite reach that mark. Probably more like 8 psi/1000 rpm, except at idle. At 800-900 rpm it's down to around 5 psi or less . This has been pretty much with straight or multi grade, syn or non-syn oils. I've been using Torco 20-50 for the most part. Of course, thinner oil flows easier. So maybe those low pressures at idle are no big deal, but I sure hate seeing the needle drop that low. Keep in mind this is with a fresh engine and a new oil pump.

JimC · Jul 9, 2012

Sorry for the redundant info. I took some time to compose my post and others posted the same information before me.

Bob Z. · Jul 9, 2012

Sometimes a worn oil pump IS some of the low flow and pressure problem.
The wide return gears show damage probably caused by metal bits that ran through the pump.

Brooking 850 · Jul 9, 2012

deleted

bill · Jul 9, 2012

this has been discussed to death and I will say it again THERE IS MORE TO IT THAN END CLEARANCE and surfacing the end plates. Gear tip to body, gear tooth to gear tooth and where the shaft's pass through the pump body to name 3 more places that WILL cause low oil pressure and faster wet sumping.

Brooking 850 said:
"What you can do is put the pump apart and check the faces on the side plates to see if they have any scoring. Usually in a circle pattern where the gears run against the plate.This is where the oil leaks past if they are bad. The cure is to get the plates and lap them on a sheet of wet n dry paper on a piece of glass till they are all smooth.

Thanks to Sir Dal!!!
Regards Mike

Brooking 850 · Jul 9, 2012

Hi Bill,
agree totally I didn't post the rest of the email , he did mention those same facts. I was relating totally to the scored end plates in the pic.
Having not been on this forum for long and it would take more than some days to read all the threads i will remove the post so it doesn't offend.
Unfortunately some of us haven't been on here ffrom the start
Regards Mike

champ7fc · Jul 9, 2012

Newly restored engine, same setup, oil pressure gauge from old brits, lapped the oil pump plates during rebuild. 40 weight aviation mineral oil. Readings cold- startup@ 75degrees ambient-60-70 lbs, cruise when warn30-40 lbs @3500-4000 rpm, oil hot @ idle 20 lbs, oil hot after long run @ 3500-4500rpm 20lbs and oli hot@ idle 10 lbs. These are all observed readings in the last week after I changed the oil @ 600 miles. The outside air temp in this area last week was 90-98 degrees . In cold weather this winter I was getting readings of 80lbs cold at startup. This is a new engine with a balanced crankshaft and all internal parts except the rods and crank replaced. I hope this info is of some help. Craig

bill · Jul 9, 2012

it was not posted to upset any one. but it get's old seeing the same thing posted over and over and some will take it as THE fix. as the discussion is on low oil pressure and wet sumping there is more to it than just lapping the end plate's therefor you might have posted the rest of his info

Brooking 850 said:
Hi Bill,
agree totally I didn't post the rest of the email , he did mention those same facts. I was relating totally to the scored end plates in the pic.
Having not been on this forum for long and it would take more than some days to read all the threads i will remove the post so it doesn't offend.
Unfortunately some of us haven't been on here ffrom the start
Regards Mike

john robert bould · Jul 10, 2012

OPRV 45 lb...how did you get 60-70 lbs :?: unless the pump produces more pressure /flow than the relief valve can dump :?:

champ7fc said:
Newly restored engine, same setup, oil pressure gauge from old brits, lapped the oil pump plates during rebuild. 40 weight aviation mineral oil. Readings cold- startup@ 75degrees ambient-60-70 lbs, cruise when warn30-40 lbs @3500-4000 rpm, oil hot @ idle 20 lbs, oil hot after long run @ 3500-4500rpm 20lbs and oli hot@ idle 10 lbs. These are all observed readings in the last week after I changed the oil @ 600 miles. The outside air temp in this area last week was 90-98 degrees . In cold weather this winter I was getting readings of 80lbs cold at startup. This is a new engine with a balanced crankshaft and all internal parts except the rods and crank replaced. I hope this info is of some help. Craig

L.A.B. · Jul 10, 2012

john robert bould said:
OPRV 45 lb...how did you get 60-70 lbs :?: unless the pump produces more pressure /flow than the relief valve can dump

The OPRV blow-off pressure can depend on how it's been set (shimmed), however I did notice that the oil viscosity does seem to affect the blow-off pressure reading.

From my own test gauge checks, the OPRV doesn't appear have any problem coping with pump output even with cold SAE 50 monograde.

The factory manual quotes a figure of 45-55 psi for the OPRV.

fredful · Jul 10, 2012

.

Well here's my two bob's worth of opinion. As Joe says he has the line for the pressure gauge connected to the left side rocker feed, and as we know pressure is dependent on flow vs resistance, so perhaps as a result of a rocker spindle fitted with the flat facing the wrong way there is not enough resistance to get a good reading. also pressure loss through the length of small diameter tube could be significant. It may be a better option to connect the pressure gauge to the banjo at the back of the timing cover or even directly at the end of the crankshaft, here's one I did earlier .

[album][/album]

SteveA · Jul 10, 2012

In my numble opinion you guys really do worry too much about oil pressure......look what fitting a guage did for you...it gave you something to worry about every time you look at it....

And that modification on a timing cover looks like a great way to get instant zero oil pressure as the pipe or joint fails! OK for a one off test, but you cant ride with that.....

Make sure your pump and crank end feed seal are in good condition by inspection!....any other method is speculation....if in doubt change both!....big end bearings should be inspected in the same way if mileage justifies it, or if you have no idea of the condition of the engine and it is noisy, after that....use a quality oil, mineral 20/50 or monograde to suit you and ambient....keep it topped up...and stop worrying....

(oops! I typed numble instead of humble, but thinking about it, am a bit 'numbled' by the constant worrying about oil pressure :roll: )

Hobot · Jul 10, 2012

More ancient text on this subject and related factors

http://www.nortonownersclub.org/support ... l-pressure

Quote from Dave, maybe DogT here?

3 o rings....
2 on the rotating main shaft,
one between the feed and scavenge side gears
and one between the scavenge gear and the drive geat.
The shaft is ground with grooves to sliding oring fit tolerances.

1 on the idler shaft between the feed and scavenge side.
This shaft is stationary and the gears turn, therefore, this
shafts is ground with a groove to stationary oring fit tolerances.

These groove tolerances are easy enough to find, sorry I don't
have the numbers readily at hand.

FWIW There are four possible wet sump leakage paths in a norton
oil pump and lapping the ends only address one....
shaft o rings address the second.
3rd = gear to gear wear
4th=gear tip to pump body wear

dave

And unknown author I saved..

The Mark III seal is thinner than the other. It has a small taper then flattens out, whereas the other has kind of a dome.

Here is what my factory manuel says Section C30 / 11 third paragraph ...Very late engines use a joint gasket between the oil pump and crankcase joint faces and where a joint washer is used at this point, under no circumstances should the conical rubber seal between the oil pump and timing cover be equiped with packing shims....

Para 13, Fit a new conical rubber oil seal part number NMT272 on the oil pump outlet stub and dispense with any shims which may been fitted between the seal and pump body at the time of dismantling. Over compression of the seal will render it unfit for further use.

It appears part of the shimming process is the paper gasket behind the oil pump, and when used with the proper seal and stub outlet, should get the proper clearances without shims.

The '75 and later 850 MkIII had a different seal that didn't require shims. All other Commandos both 750 and 850 used the conical seal and required checking to make sure there is compression. The amount of compression is just enough to make a seal, don't completely flatten the seal. The doubt I have is .020" is a lot of shim and I haven't needed shims in the past. Better to check again and waste the seals. Then on to the blown crankshaft seal in the primary.

Just one more word of caution about eliminating gaskets: the oil pump gasket is .007" thick, so eliminating it will reduce the compression on the oil pump seal by this same amount. This could mean the difference between adding shims or not on the older twin chain motors. Or, possibly an ineffective seal if shims aren't used to make up the gap.

There are 4 things to consider in seal fit of pump to TS cover. oil pump/crankcase wispy gasket, shim under pump nipple, thickness of pump nipple and thickness of TS cover gasket. Here's the recommended combo for all Norton twins below.

Walridge Motors catalog:

Note - Later, thicker Commando type timing cover gasket [06-1092] is recommended for use on all 500-850 twins, but MUST be used in conjunction with oil pump gasket 06-2447 to ensure correct positioning of the oil pump vs timing cover.
Timing Cover all yrs, p/n 06-1092
Oil Pump all yrs, p/n 06-2447
Oil Junction block all yrs p/n 03-2044

And a review of the Service Notes comment on significance of oil gauge fright.
http://www.billymegawatt.com/uploads/6/ ... _notes.pdf

Mention of pressure brings me to another point-the fitting of oil pressure gauges. On the Commando (and for similar reasons. most bikes) an oil pressure gauge is more of a liability than an asset. It is of necessity, fitted on the feed side where any failure of pipe or gauge is disastrous to engine and rider--it’s touch and go whether the engine seizes before or after you fall off with oil on the back wheel. On the Commando this failure could be caused by engine
vibration in the same way that early rocker pipes failed. (We’re coming to that.) The other reason that a pressure gauge isn’t much good is really twofold. At high speeds and high oil temperatures the pressure can drop to nothing
on the gauge because the pump can hardly keep up with the rate the stuff is flying out of the big ends. The centrifugal force can keep the pressure at the big ends above the danger point, so there’s no real panic--but the gauge
would inspire you with horror. Then of course if you did seize an oil pump by the time you noticed that the pressure had dropped the big ends would have gone (. . . through the hole in the crankcase, with average N.O.C. luck!). If you
want an interesting gauge to frighten yourself with, but, which is inherently safer and can give useful information, fit an oil temperature gauge in the oil tank. Let me know what it reads as you change into top for the Mountain Mile on
both the fourth or fifth lap! The latest Racing Nortons (we can’t call them J.P. Nortons any more as they’ve stopped the bikes from smoking) had a new type of oil pump-I wonder if this is because the ordinary pump can’t keep up?

Hobot · Jul 10, 2012

Its pleasing that Commandos are mainstream market enough even JCW carries a gauge section labeled for Norton;

http://www.jcwhitney.com/gauges/norton- ... j1s21.jcwx

DogT · Jul 10, 2012

Brooking 850 said:
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

ludwig showed a picture of a setup he made not real long ago. Search his posts and I'm sure you'll find it.

Dave
69S

Brooking 850 · Jul 10, 2012

thanks Dave will do a search
Regards Mike

Hungry J0e · Jul 11, 2012

Well guys, thanks for all the posts.

Removing the timing cover is definitely in order. Chatted with Fred and Old Britts and he gave similar advice as many on this thread... pull the timing cover, inspect the crank oil seal and the oil gasket. Based on the fact that my primary crank seal was in *backwards* would be no surprise to see the same here.

As far as the oil pump, I don't feel I have enough expertise to know the difference between a decent pump and a pump with worn out gear teeth (although obvious scoring, etc. will surely be apparent even to a guy like me). While the timing cover is off, I'd like to send the whole thing off to AMR to have the Nortec anti-sump upgrade installed... part of the service includes disassembly and inspection of the oil pump so they should be able to alert me if a new pump is in order (hopefully not... not cheap!).

Will most likely fit new timing crank seal and oil pump gasket on reassembly... have the oil seal guide on order...

Will post my findings.

Cheers,

- HJ

dynodave · Jul 11, 2012

You can't do a full AMR upgrade to a MKIII. Only the pump mods can be done...and why bother if the pump is dead? The first thing to try is pull out the piston and pull the piston/spring out and polish it with crocus cloth and then buff it to a mirror finish and clean the bore up in the timng cover. That should improve the wet sumping but won't do a thing for a dead pump and neither will the AMR mod....
Honestly, I know of no one in the world who has bothered to make an oil pump test rig until...I did. I would assume the original maker of the pump does, but I would bet a substantial amount of money it is NOT NA. I will eventually have a testing procedure down and specs too....My data and test procedures are a bit too crude for my satisfaction so far.... and I can't commit the time at present for such a low priority project .

Oil Pressure Gauge

Reggie

Hobot

JimC

JimC

Bob Z.

Brooking 850

bill

Brooking 850

champ7fc

bill

john robert bould

L.A.B.

Moderator

fredful

SteveA

Hobot

Hobot

DogT

Brooking 850

Hungry J0e

dynodave

Similar threads