1952 oil pump

[anjimehra]

Hi
Back on working on the A7 after a gap of 10 weeks on the road in the high Himalayas.
A question. How does one check if oil pump delivering correct pressure. The valve gear noise persists. Although oil is coming up to the rockers, I think pressure too low to lubricate tappets. If Iam right, cam gets lubricated when the pressure valve lifts & oil is diverted to the cam Lub gallery & also lubricates the timing gears en route.
Also, if oil is returning to tank, then pump must be working , but at what pressure ?
Any suggestions. Thanks
Anji

[JulianS]

No easy way to check pressure I can think of. It depends on the condition of your oil pump, pressure valve and fit of main bearing bush and bigends.

The 1956 type oil pump gives better oil feed.

The cam and followers are also lubricated by oil draining from the inlet rocker box

[muskrat]

G'day Anji.
You could test the pumping pressure (not the blow off pressure) by modifying a pvr. Remove the ball & spring, block the blow off holes and drill and tap the end to take a fitting for a gauge. This will tell you what the pump is capable of.
Cheers

[Sluggo]

When I worked for a shop & Dealership some years back (We worked on all kinds of classic bikes but were also a dealership for new Enfields and Urals) we had a test station to proof and test oil pumps.  It was surprising what can result. I thought the original Enfield oil pumps were a joke and was very pleased that starting with the Electra models they went to a real oil pump which I believe helped immensely.

  I made up one for Triumph twin engines and loaned it out for a vintage bike meet and someone stole it, have not made a new one yet.    I was thinking that with a number of BSAs i own, both preunit and unit models and the dodgy reputation that BSA pumps have that it might be a worthwhile project to make a test rig for BSA pumps that can accommodate a variety of pumps.  Might be a good off season project.  Ill post pix of my alternator and stator test rig as well, I am expanding it to test coils, and regulator/rectifiers

But there is a number of people who have done the same,. This article is quite interesting... I have a 1962 Matchless G80CS as well, and came across this article some time ago and thought it was worthwhile.  The oil pumps for later versions are the same as many Norton models so there is a cross over..

See: http://centralcoastclassicmc.com/NortonOilPumps.htm

Noc has a thing or 2 to say on the topic: http://www.nortonownersclub.org/support/technical-support-common/oil-pump-repair

Not related to BSA, but a wealth of knowledge and excellent tech materials posted by Fred & Ella up North of me in Seattle.  (Been a real asset to the community)
See: http://www.oldbritts.com/ob_tech.html

DynoDave also does BSAs,, but has written a wealth of info on a wide variety of topics, mostly related to Nortons as we all know,,, they need all the help they can get. 
But he has posted on a variety of forums the wide disparity of performance in rotary style oil pumps (Usually Norton) but the same design applies to BSA.  He has written some posts on this as well on AccessNorton and INOA about how BAD some pumps are and cautions anyone to test your pumps. Never assume.  The material he has posted has made me a believer.  You can troll around forums looking for his postings but here is his own main website.

See: http://atlanticgreen.com/norton.htm
See: http://atlanticgreen.com/bsamain.htm

I do have a couple cast iron pumps for the 1971-73 Unit twins and a B50 Single and I really like those, Thats what BSA Should have made all along.  But any pump can be improved.  Personally I am a BIG fan of a liquid filled oil pressure gauge and I tend to fit one to any of my bikes I keep for myself.  I am not certain yet how to plumb them to a preunit A10 but I will be doing so at some point.

I firmly believe it makes you a better owner and operator, Cold pressure can be shockingly high and it encourages you to properly warm up your mount, as well as prevented a few catastrophes.  Ill spare you the tales as the examples I have are NON-BSA but the experiences compel me to fit a gauge to anything I get my hands on.

I have a number of BSA service bulletins and its amusing how they decided to eliminate the idiot warning lights on later unit model BSAs because they alarmed the owners and resulted in more service warranty claims.  But my take-away from that is that Ignorance is NOT Bliss!

[anjimehra]

G'day Anji.
You could test the pumping pressure (not the blow off pressure) by modifying a pvr. Remove the ball & spring, block the blow off holes and drill and tap the end to take a fitting for a gauge. This will tell you what the pump is capable of.
Cheers

Hi Muskrat
Thanks. Got an adapted made to fit the bigger body of the prv. Also, what should the pressure be on a cold engine.

[muskrat]

G'day Anji.
I haven't actually done that test. My guesstamate at a fast idle with 25/50 oil cold, would be around the 60 to 70 psi. Hot that would drop to about 15 to 20 psi and should get to 50 psi by 2500 rpm.
Please post your findings either good or not so good. I'll try to run a test soon.
Cheers

[JulianS]

Not seen a figure for A7 or A10 but BSA did publish one for the A65, page 2 of that bulletin attached.

[muskrat]

G'day Anji.
Just did a test on my 51 A7 (I wish I hadn't, rebuild will be sooner rather than later) and 57 A10 (recent rebuild). I plugged the blow off holes with blind rivets in the main body and drilled & tapped the end cap to take the gauge fittings.
  The A7 was very worrying (it's not fitted with a full time gauge like the A10). I know the main bush is worn but it must be phu(ked. At best it might have shown 5 psi at fast idle and maybe 10 psi with revs  .
  Then before I put the same setup on the A10 I started it for a minute to get the oil through it, 55 psi at fast idle. I then changed it over to the test rig. Strange that at the same fast idle (1500 rpm) it only showed 25 psi  . I then took her up to 4000 rpm (not wanting to rev a cold motor with forged pistons) and saw 90 psi on the gauge. It's fitted with the roller conversion and end feed to the crank so there's no loss through the bush.
  Now that my A7 is a lot sicker than I thought she'll be up for a rebuild over the next few months (after I move house), and she'll be getting a full time oil gauge. Lucky I did the test, she could have thrown a leg out of bed.
  Let us know your results.
Cheers

[Black Sheep]

I do wonder where this myth arose about loss of oil pressure from a worn timing side bush causing big ends to seize and throw rods? I have NEVER come across this and I have been involved with BSA twins since 1972. The spinning crank draws oil in through centifrugral force so as long as there is oil getting to the bush, some will get to the big ends. When a bush gets that worn, the big ends will be similarly worn as well and a knocking noise is what alerts you to the fact that it's time for an overhaul.
Norton twins were at first fitted with an oil pressure gauge. With a modest barrage of complaints of low oil pressure, a press demonstration was arranged with a 500 Dominator engine under full bore with no oil pump fitted - just a gravity feed to the crank from an oil tank. I think it ran for a full 24 hrs and had no discernable wear on strip down. Norton then ceased fitting oil pressure gauges.
Rods break from fatigue failures precipitated by long periods of high rpm.   

[muskrat]

G'day Black Sheep.
I beg to differ, the oil has to fight centrifugal force to enter the crankshaft in the first place. If there is enough clearance in the bush (about 8 thou in this case) it will take the easy way out. Starving the big ends, spin a bearing and self destruction isn't far away.
I'm not taking the chance.
Cheers

[Sluggo]

Im going to go with Muskrat here,  That is the advantage of a quill feed on the ends vs feeding a spinning crank thru a grooved channel and small holes in the crank at speed.

Its also well established that a needle or roller bearing requires far less oil than a plan bushing, and can suffice on splash,  Not only is there plenty of SAE and other engineering papers on this, its also empirical evidence in models fitted.   IE: 441-B50 vs B25/T25. in the rod bearings. 

I can say, in dealing a very significant volume of British bike parts in my own shop & business that in my own personal experiences the volume of drive side rods ventilating cases on a BSA twin is approx 4-1 compared to Triumph and 3-1 on Nortons.   I believe and well supported in a lot of literature that the Triumph plunger type oil pump has far less issues than the gear type pumps in Nortons & BSA..
But the rods that break or go thru cases are the furthest from the oil supply in almost every single case.
While rod fatigue IS a issue and I rant about service life a lot, the cause of the calamity is seized rod bearings on the crank mains.

One of the most overlooked aspects of these engines is FLOW is far more important than pressure. Volume is the key.  Pressure is merely a reflection of friction and resistance, and while a pressure gauge is an important indicator of whats going on, Its not feasible to fit  a GPM or flow measurement onto a motorcycle.
(its more a math equation anyway).   

There is a sweet spot of the speed and pressure that a oll flows past a bearing or surface, not only to maintain the barrier of lubricant between to moving metal surfaces but the important cooling effect. Too fast and it does not carry away the heat.  But the proble with many oils and especially the old straight weights is that until they reach optimum temp and viscosity, they result in too high of pressures, lack of flow, friction and wear.  It is NOT  myth that most engine wear is at start up.  I have a oil gauge that only went up to 80 psi and it was damaged on a Norton as the pressure went up to 120 at start up and the gauge was damaged.   

As to running with out oil, an engine CAN run for a long time under the right circumstances without lube,, in the US at fairs, and large public events its quite common or used to be for sellers of snake oil and similar miracles in a bottle with have a running engine without a oil pan or any lube chugging away for hours on end to demonstrate the wonders of their miracle product.  But you wouldnt get very far on the interstate trying that.

Another common myth that drives me batty is people with a worn engine (Smoker) who add a thicker viscosity to get by or "Tighten up" the clearances.  In reality all you are doing is accelerating wear.  Pressure will go up but flow and volume goes down.

Around 1990 I had a opportunity to spend some time with some pro race teams, IRL-CART-Indy cars and I could care less about the drivers but instead interviewed the crews.  Bobby Rahals team had a big sponsorship deal from Penzoil at the time and they had transitioned from DINO oil to synthetics.  During this time most teams were running the Chevrolet Illmore engines and the cost of each engine was over a million dollars.   During testing with the synthetic the crew chief and head engine guy told me they were alarmed by the dramatic loss of pressure. They got on a teleconference right away with the Oil company.  They were told by the engineers at the oil company that this was normal and expected and a good thing. (Flow & Volume vs pressure) the clinched the discussion with the promise that if the team lost an engine due to oil issues that the oil company would buy the engines.  End of discussion and they told me their costs went down and they did not lose ANY engines for oil failures.   These were not marketing people telling me this, this was the crew.  Sold me!!!

[BSA_54A10]

I do wonder where this myth arose about loss of oil pressure from a worn timing side bush causing big ends to seize and throw rods? I have NEVER come across this and I have been involved with BSA twins since 1972. The spinning crank draws oil in through centifrugral force so as long as there is oil getting to the bush, some will get to the big ends. When a bush gets that worn, the big ends will be similarly worn as well and a knocking noise is what alerts you to the fact that it's time for an overhaul.
Norton twins were at first fitted with an oil pressure gauge. With a modest barrage of complaints of low oil pressure, a press demonstration was arranged with a 500 Dominator engine under full bore with no oil pump fitted - just a gravity feed to the crank from an oil tank. I think it ran for a full 24 hrs and had no discernable wear on strip down. Norton then ceased fitting oil pressure gauges.
Rods break from fatigue failures precipitated by long periods of high rpm.

Never seen one in OZ
Nearly all reports came from the USA where there are roads where you only turn twice between filling the tank.
Once to turn out of the servo and the second to turn into the next one.

However I have my doubts that the main bearing is the actual cause of the failure as I ran my A65 with stuffed bush for 10 years till the oil pressure light was on at 3500 rpm.
Big ends were definately worn but not to the point of seizure & failure.

I put down rod throwing to ring flutter at WFO tossing the oil out the exhaust.
My bikes got run quite hard and we used to drag nearly every Friday night along the breakwater for the yet to be finished Port Botany.
After a few 2 mile hard runs there was a lot of oil in mufflers to the point it would drip out and make a bigger puddle than from the primary.
Add to that all of the oil blown out of the breather tube and I have always felt it was lack of oil more than low pressure that locks up the big end.
To this extent I have noticed that all of the welded up cases I have seen were on Spitfires & Lightning but never on a Thunderbolt.

My theory was somewhat reinforced when I was sent to recover a new Triumph from a farm.
The owner was in a group of riders on an interstate ride when they got pulled over for an RBT , rego & license test, the latter of which he did not have.
This resulted in a somewhat spirited persuit by the local HWP and in his story he mentioned that he had to continually turn the bike off the on again as the rev limiter kept cutting the engine off.
When I pushed the bike up into the van ( van in case the buys recognised the bike ) oil literally poured out of the muffler and when I got it back to hime & we looked at it carefully, the engine was locked solid and there was not a drop of oil in the engine.
So while he got away from the blue boys, avoiding a "free holiday" it was not without cost and the 3 year old bike was a write off. 

[duTch]

 

............ as the rev limiter kept cutting the engine off....

      ...like a governor ?

 So just exactly is the difference between a '52 oil pump and later A7/10 ones, apart from I believe the 'high flow' one I bought is probably just a A50/65 one with wider gears and A7/10 drive, but that's probably a different story.

 Just curious, as my engine is stamped 23/12/52 so a '53 model BA ****

[JulianS]

Different tooth form, less teeth  on the 1956.

Photo 1 is the service sheet which introduced the new pump.

Photo 2 is a 1956 on type

[duTch]

 Ah yes, I now remember discussion on that a while ago