The big end bearing in a BSA single is an 'open' unpressurised roller bearing, so unlike white metal shells does not require a high pressure to function correctly...
Volume is the most important thing. The anti drain valve ball will lift of its seat at approx. 7psi and then allow oil feed to the engine and this occurs virtually instantly when the engine is started up....
Against a 'blind' gallery the pump is capable of generating very high pressures but you will not see this during normal operation...
The 'spit and bubble' oil return is purely the result of the fact the engine is a dry sump type and therefore the pump has a greater capacity on the return side than the feed side to ensure the crankcase is scavenged...Ian
email (option): ian@wright52.plus.com
As an example of volume at a given rpm. 1/2 a pint per minute at 2750 rpm would be typical...But you will need an oil pump test rig to measure it as there is no rev counter on an M20! (also to do a true comparison through the rev. range you will need an original NOS pump)
I've never had a problem with a deficiency in oil delivery on any B or M Series type pump...
Some test results obtained by a friend of mine from a number of used pumps produced pretty good results when compared to a NOS one...Ian
email (option): ian@wright52.plus.com
No, not really...there is little oil returning on the return side to compare, or at least, no actual flow once the crankcase is empty.....As stated previously these are dry sump engines and therefore they scavenge the crankcase , so there is only an intermittent oil return....
A bike which is run regularly will have little oil in the crankcase and therefore only a 'spit and bubble' return 'flow'...
Bikes which are not running regularly will, depending on the condition of the anti drain valves, oil pump and the duration of the time they have been standing, have differing amounts of oil in the crankcases and will return oil as a continuous flow for different durations until the cases are scavenged...
Even if a direct comparison between two bikes had the potential to produce an accurate conclusion, which using a basic visual comparison it doesn't, both engines would have to be running at the same rpm. when making that comparison and with no accurate rev counter that can't be verified...
Further..any result should be measured against a 'control' or known quantity...In the case of the tests I was involved in, that was a NOS pump.
The comparison you are proposing is only comparing one worn pump with another, so wouldn't provide an answer ref. either pumps actual efficiency set against the optimum figure produced by a new pump...
Consequently this isn't a viable method of testing....
It will only give a generalised indication of the operation of the return side of the system (basically just confirming it is working) and will tell you nothing at all about the performance of the completely separate feed side, other than the fact it is working as well and is capable of providing something to be returned to the tank....Ian
email (option): ian@wright52.plus.com
Didn't many vintage bikes have big ends fed by a total loss system with the oil flow measured in "Drops per Minute"? Seems to me that if the oil is flowing rather than dripping you don't have much to worry about.
Cheers
Pete
email (option): petercomley@web.de
True to a degree...but even with that system, if the manufacturers pump settings were used a given volume of oil per minute was delivered to the engine..Ian
email (option): ian@wright52.plus.com
Hi John, that's what I have on my WM20, with an anti-wet sump valve.
YouTube has shrunk it, so go "Full screen"
(Copy and past the below link into the browser)
https://www.youtube.com/watch?v=Gw_UHLf_FGE&feature=youtu.be
By the way, I saw few cases (And I guess that most of you have seen many more than me..)
where the "Bigend" bearing oil pass was completely clogged with tar,
So basically, if oil cannot go out of it, then new oil cannot enter,
And still, the bearing looked ok, not much slack, not "blue" of heat..
Noam.
email (option): noam10@gmail.com
Hi John,
If you apply air or oil pressure into the main shaft, Timing side,
And everything is clear and opened, then this pressure should pass
Through the main shaft, from there through the flywheel, and then through
Parallel hole/passage > from the flywheel's timing side into the bearing,
and out to the sump.
(You can even try to blow air with the mouth, or oil with an oiler, with the nipple pressed against the drill in the shaft)
If a pressure is built when you apply it, and does not pass and relived,
Then most probably there is a clog along the way.
This is the way I check it, anyway..
if the bearing is blocked, then the only way to open it, as far as I know,
Is to open the motor and open a screw plug on the bigend bearing, clean it, and close..
(See screw on first photo)
I took some photos.
The hole on the right end of the pin, on the ramp, is receiving the oil from the flywheel,
and the others, in the middle, are the oil exit holes, into the rollers.
By the way, the results you got when comparing with Ron are more or less
The same as in the YouTube link of my bike, which I sent in the previous reply?.. 
Cheers,
Noam.
email (option): noam10@gmail.com
John showed me a picture from the guy who made the tell tales. Showing an oil pressure gauge fitted to the lower crankcase blanking plug and giving a reading of 2.8 bar (40psi) at about 2000 revs (I think). I would not have expected such a pressure Ron
email (option): ronpier@talk21.com
The pump will generate those sort of pressures when pumping against a 'blind' hole...In fact it will generate higher pressures than that.
The A10, for example, uses a very similar pump to generate the high oil pressures required for its white metal, shell bearing big ends..
However, those figures are not indicative of what is happening under normal operating conditions in an engine with a roller big end...Operating pressures in those types are far lower....and remember that pressure and volume are not the same thing...
A measurement of the pumps pressure capabilities against a blind hole cannot be converted into a figure that accurately quantifies its ability to deliver a given volume in a given time at a given rpm....
As the system relies more on volume than pressure it is best to measure that rather than to become fixated about oil pressure...
During the late 30s Ariel removed the oil pressure gauges from their singles largely because of warranty problems arising from owners thinking the oil pressure was too low and/or noting the natural fluctuations of pressure with revs and engine operating temperatures...
The bikes themselves were working fine and delivering sufficient volumes of oil....Needless to say that move resulted in a lot less warranty work....Ian
email (option): ian@wright52.plus.com
I too think the the oil pressure should be a LOT lower than 40psi, for the reasons Ian states. But as the bike with the high pressure is not the OP's then I wouldn't worry about it!
Most of us will not have facility or technology to measure the flow of oil reaching our bearings. The best we can usually do is determine that the oil is at least circulating. If it's returning to the oil tank, it must have been delivered to the engine in the first place. Of coarse a blocked gallery along the way might still allow oil to return without reaching all the parts
Like the new big end that was fitted by a well known dealer to the Ariel W/NG project that I bought from him. It had been fitted the wrong way round so that the oil receiving hole (as in Noam's) picture was in the wrong fly wheel. I wonder how far I would have got on a pre lubricated big end if I hadn't spotted it.
Ron
email (option): ronpier@talk21.com
I agree..It's either some rudimentary checks during rebuilding and in the early stages of running, to ensure oil is circulating.... or...
It's setting up to thoroughly test the performance of the pump(s) in a meaningful and well thought out way if a more in depth picture is required...
Beyond careful assembly of the pump and those initial simple checks I think there is little point in worrying about how things are working...Particularly so with an M20 oil pump where failures are virtually unheard of...
In 40 years I've never had one fail to perform as required....Ian
email (option): ian@wright52.plus.com