oil pressure gauge

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Apr 15, 2004
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Was reading a technical article on OldBritts about the oil scavenging problem on 72 750 motors. I'm worried because my bike has a 72 motor which is subject to the problem he describes.

So I think installing an oil pressure gauge on my bike would be a really good idea. Their kit looks very clean BTW, I'm thinking of buying it. But they mention that "a lot has been written about oil pressure gauges on Commandos." Apparently there's some controversy about whether or not it's a good idea to fit them? Does anyone know anything about that? It's hard for me to understand why I wouldn't want an oil pressure gauge. Could save me from a destroyed engine. But I don't know. Other people who presumably know a lot more than I do seem to think it's a bad idea???

So I'd like to hear some opinions on this...

71 750 Roadster with 72 750 engine

It appalls me every time I'm reminded that a Norton has no oil pressure gage or light. What could be more crucial to the health of an engine than proper lubrication?

I think installing an oil pressure gage is a great idea!

Debby, Fitting a gauge will not break a motor. But the data shown by the gauge may be only relative to the top end oil system. Most people fitting a gauge pull the the line from a banjo fitting in the rocker spindle oiling system. This does not really show what's happening at the crank. It does give an idea of the thickness of the oil in the bike as it gets hotter you do see a drop in the pressure. A oil temp gauge may give better data. Both would also be an option. If one could know that the pressure on the crank was running 10lbs per 1000 rpm that would be good but it's not that easy to get that pressure because of plumbing. A pressure gauge off the top end still is a good piece of mind accesory and I run them on my bikes and use the info more like a temp gauge than a pressure gadge.
The oil pick up problem on72 cases stems from the moving of the pump pick up point. It was moved forward in the case. Now the oil coming off the crank has air in it and the pump has to move this airated oil and that causes loss of pressure. This can be fixed and I have done mine but it does require the splitting of the cases. The fix is spelled out in the Tech Digest. If you only have a small drain bolt and not a large sump on the bottom of your cases you have this system. This is a problem at high rpms for long runs and is not some thing to go nuts over. But it is good to do when retrofitting super blend crank bearings, a winter project if you will.
I have built my own pressure gauge holder that uses the smaller oil filled 100lb black face gauges here are some pictures. As always just keep hitting the next button to get through the four or so pictures. http://groups.msn.com/Brit-Fe-Pics/shoe ... hotoID=158 norbsa P.S. I thought I heard a D in there.

DynoDave has it exactly right. You need oil FLOW, not pressure. Pressure is what causes flow, and can change drastically over temperature, and the wear in the machinery. If you do put a gauge in, don't be alarmed when it reads quite low with a warm machine. We would probably be better off if we had a "flow sight glass" somewhere that we could readily see it while operating the machine. Also be aware that just because you have pressure, you do NOT necessarily have flow. A flow restriction in the system will allow the pressure to rise to the max capability of the oil pump, but those components beyond the point of restriction will be starved for oil FLOW.

INOA 2327
64 Featherlastic
You know, all I really want is an oil pressure warning light like on my other bikes. My main concern is losing the oil supply to the top end when I'm riding down the highway and not realizing it until the engine blows. My engine is one of the ones (small drain plug, no big sump plug) that's susceptible to that. So they say anyway.

Was thinking: oil pressure switches for my Suzuki 550 are still available. They cost $15. I wonder how hard it would be to fit something like that to the rocker feed banjo bolt? I could wire it up to the assimilator warning light which is unused on my bike as it has no assimilator. Then if I saw the light come on I'd know I should slow down or call for a truck or something...

The gauge does sound interesting but it's expensive and is overkill for my needs.

Or, another option: sell the stupid bike and get an 850! I'm continually dismayed to learn about all the design deficiencies my bike has that were corrected on the 850. Blah.

Hi Deb,

Norbsa's oil pressure gage looks pretty nice to me. I've seen other Norton riders rig up similar systems. I really think an oil pressure gage may be easier to install than a oil pressure light.


oil pressure thingy

after reading all the threads, Ill never be able to spell the G-word correctly again! :?

I see what you mean: we have "gauge", "gadge" and "gage"!

Interesting, I'll take the hit for "gage". But actually, "gage" is a variant of "gauge". I've always used "gage" for round things with dials. And I use "gauge" when I refer to the thickness of wire or sheet metal, or even a shot gun, as in 12 gauge.

Now for "gadge"; I can't quite figure out the logic for this spelling other than it came from Norbsa. He's probably too cerebral to worry about such minutia as the spelling of "gage."


'72 750 oil pressure

Hi Debby,

7 years ago when rebuilding my '72, I decided to do the oil pickup modification and convert to an 850 engine breather location. Looking back on it, I really don't see any "improvement". I've never heard of a combat engine being destroyed due to the original oiling system or engine breather setup. Some say more oil goes up the combat breather than the oil return line. Sounds like a good thing to me!

One bad thing about the '72 - '73 engine cases is the loss of the oil sump screen. If an errant metal piece gets sucked up the intake it goes right through the oil pump gears instead of through a screen first. Piston fragments are what killed the original pump on my engine....previous owner's destruction. Adding a spin on oil filter is a good idea, but won't protect the oil pump from this scenario.

Having recently split my 72 cases, I also thought about the Old Britts article.

The machining of the cases did seem to make lots of sense for the oil pickup. But then I reread the article again & thought, well, my bike is never going to the type of constant high revs that Freds' race bike probably gets. So, I did not bother.

Personally, I have had 4 1972 "Combats", ridden them "hard" in my earlier days & not had a problem that it would have "fixed".

As far as an oil pressure guage goes, it will only be of use if you keep a vigilant eye on it anyway.

Keeping a check on your oil level, connections & regularly changing it should keep the oil flowing. If it gives you more piece of mind , you may as well do it though as it can't hurt.

Watch out that your "Rocker Feed line" is not contacting any hot surfaces, as this can melt and..............Just a thought as you probably have yet to experience a rocker feed "melt down".

That is my response to your question above, wasn't logged in as I have cleaned out the cookie jar.

In Australia, we have a mini "Sturgiss" called Gold Coast Bike week.
It has 2 days to go.
Check it out, if you are interested.


Just about to head off, clear blue sky & 27 degrees.
It should be a great day for bikes.

Thanks guys, that sounds reassuring. Was worried about facing an extremely expensive engine teardown/rebuild. I like the looks of the OldBritts gauge kit though, still might get it. And I like the idea of getting an early warning if the oil pressure does go to zero.

Reg, enjoy the bike week. Looks just like Las Vegas! And how about that crazy guy with the jet bike?!


Sorry for the late response on this subject... I'm in the middle of the Arizona desert right now.

In stalling an oil pressure gauge saved my engine!!! It surely would have blown by now had the lack of oil pressure gone unnoticed. As far as the crank case mod goes, I've not done it and I've riden many miles with the engine wound out (call it "Combat Syndrome" - I think norbsa has the same affliction) and I have never seen the oil pressure waver.

For those bikes that come into the shop with no gauge, I have made a gauge adapter that replaces one of the rocker feed banjo bolts, so that the oil pressure can at least be checked.


sounds like I should get one fitted.

Derek, what caused your low oil pressure problem and what did you do to fix it? Inquiring minds want to know.

The plug was missing from the cross drilling in the timing cover. For the complete story, see page 7 of the visuals section, mine is the first bike on the page :)


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