UL oil pressuree

[Martin Pettingell]

Hi all
Sorry this is something of an old chestnut but I just wanted to run it past the forum for some thoughts.
I have a 47 UL. Engine rebuilt about a decade ago, not by me. The bike seems to run fine.
I use straight 50weight oil
Recently the oil warning light has started coming on at tickover. Especially if the bike has run for a while at constant speed. Say 50 miles at a steady 50 mph or thereabouts.
I can see I have flow at tickover from viewing the top of the oil tank.
I wanted the check the pressure so took off the switch and fitted an oil pressure gauge.
Right now in the UK it’s pretty warm. Air temperature was about 25 degrees at 9.30 am
I started the bike and the gauge was showing around 20 pounds pressure at tickover. After a half hour run in mixed traffic the gauge showed zero pressure at tickover although I still had flow.
Even on a warm day I was expecting to see 3 or 4 pounds pressure when idling.
Am I being optimistic?
My feeling is that the feed pump may need freshening up. I have seen a lot of stuff written about the multi vane pump upgrades but my bike is bone stock and I plan on keeping it that way so I’m not sure that is the answer. Has any body experience of those on a stock motor?
I’m not sure what the wear tolerances on the vanes is and what too look for in terms of wear when I take the pump off and what parts could sensibly be replaced to improve it?
I’m only looking for a small improvement in pressure. Just enough to keep the oil light off and my anxiety levels down!
I am assuming of course that the problem is the feed pump and not something more fundamental in the engine
I’d greatly appreciate any input on the subject.
Thanks
Martin

[larry]

Do you have the pump with the bypass?

[Martin Pettingell]

Larry,
I believe so. It is the style of pump with the two check valves and the pump rotor has the little plunger that’s sits under the vanes.
I should have added that the pressure regulating adjustment screw was set the the correct height but one of the early things I changed was to screw this in a tad to just increase the pressure. It is my understanding however that this adjustment simply redirected more oil to the crankcase rather than increased the pressure overall - but I’m not sure of that.

Regards
Martin

[larry]

The pressure relief valve opens only if pressure exceeds the set limit. It is not your problem. The little plunger is the centrifugal bypass. It reduces supply to the crankpin at low engine speeds. If you have modern oil control rings, it is unnecessary and can be disabled by installing a larger spring at the check valve (the one for the bypass, not the other). The service manual has a very good diagram of the system.

A typical place to lose pressure is at the pump gasket. It must be only thick enough to keep the rotor from binding.

I suspect your pump is simply worn. It may be difficult to improve performance. A lubrication system that is up to spec will produce double digit pressures at all times. However, many systems perform like yours and the engines seem not to care.

[Martin Pettingell]

Thanks Larry.
It’s a while since I had the pump apart but as I recall I refitted it with a repro standard paper gasket.
The pistons are fitted with two compression and one oil ring each and I expect they were renewed when the engine was rebuilt previously.
Am I correct in thinking that the check valve that would have the larger spring is the one that sits up next to the pressure regulating valve?
I will pull the pump off in due course and go through it again.
I see repro oils feed pumps for flatheads on the market but I have no experience of them and have never met anybody running one on their bike. I have never seen a a review of one either. All of which seems to suggest that thy are not the answer.
If you don’t mind me asking is this the Larry from the Oldtimers Club in Holland?
Thanks again for the input and advice
Regards
Martin

[larry]

Reproduction pump gaskets are often three times thicker than they should be. Yes, the check valve is next to the relief valve. I would avoid reproduction pumps. I've never been to Holland.

[Martin Pettingell]

Thanks Larry, that’s useful.
Clearly not the same guy I met at the AMCA rally in May.
Appreciate your comments and help
Regards
Martin

[Steve Slocombe]

Dear Martin, we have another UK member with a UL who has had the same anxiety, upgraded his pump, and is very happy with the results. I'll try to put you two in touch.

[Martin Pettingell]

Thanks Steve,

That would be very helpful

Regards

Martin

[kitabel]

The flathead pumps are very durable, unusual to find wear. The most likely leak is the pilot shaft bushing in the cam cover, which (if replaced) should be reamed to size with the right case and cover assembled. No practical way to cure this.
It's probably safe the way it is.
Are your baffles still in place?

[Martin Pettingell]

Thanks for this input. since the thread started I dropped the oil pump off. I found when I last fitted it that I had used a repro (not sure which make) fibre or rubber gasket.

In any event it was significantly thicker than the OEM paper version that I also had in the drawer. Not sure why I didn't use it at the time!

I understand that the pump is likely to lose pressure if the gasket is too thick so this may have been part of the problem.

I have also run up a fitting that allows me to keep the oil pressure gauge and the idiot light at the same time. Its a little cumbersome but mostly hidden behind the rear pot exhaust down pipe,

The bike has a stock (repro) type exhaust system but the muffler is an old cigar shape from a later pan or similar. It certainly has baffles in it and when running the bike is only marginally noisier than the old muffler with the pinched in tail at the end ( I have one but it is a modern repro and I prefer the rather more crusty original cigar shape)

All I need to do now is get the bike out on the road and see whether the thinner OEM gasket will have made a difference.

thanks again

Martin

[Martin Pettingell]

Thanks for the input.

Since I started the post I have pulled off the oil pump and found that I had fitted a repro gasket. Not sure which make but much thicker than the original paper version that I also had in the drawer. Not sure now why I didn't use it at the time!. I forget the exact measurement but I recall the OEM one was around half the thickness.

I have also run up a fitting that allows the OP gauge and warning light to be run together. its a little cumbersome but mostly hidden behind the rear pot exhaust pipe.

The bike is fitted with a later cigar shaped muffler - looks as though it came off a pan. Not sure if its OEM or just an old repro but it certainly has baffles and when running makes not much more noise that an original period flathead muffler.

The only thing I haven had time to do is take the bike out on a run and see whether the new gasket has improved matters.

Will post again when I get some road time.

Regards

Martin