Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65: another oil pressure thread....

hey guys- i know this topic has been talked to death, but the search function on this site makes it very difficult to turn up old info. if anyone can post links to old threads, please do. otherwise, forgive me for the redundancy.

as some of you know, i recently rebuilt the engine in my 1971 A65T. some of you might also remember that i bought it from a member here, who came posting about low oil-pressure and a knocking sound once warmed up. upon disassembly, it appeared that the classic timing side crank bush was the culprit. all bushings and bearings were replaced, and all clearances are perfect. the oil pump is alloy, but looked very good on the inside. the PRV is the domed type.

the problem: once the bike gets nice and warm, the oil pressure light starts coming on well above idle. i could be paranoid, but i feel like the reciprocating sounds in th engine also got a little louder under these conditions. i'm worried about a lack of oiling (obviously), and want to make sure the pump and PRV are working properly.

first off, i remember reading references on here to problems with the PRV and gaskets.. can someone point me in the right direction? i'd hate to kill an engine i just put some much work into rebuilding, so i'd like to know everything's working right.

I wouldn't rely on a warning light, in this situation especially you need a gauge so as to see what it does above the 7psi or so the light switches at. What grade of oil are you using? Sometimes after sitting a long time the relief valve spring can collaps, becoming short and cause low pressure, they have a set length, and can be stretched easily back to size forcing a little screwdriver shaft between the coils, you don't want too much pressure though 80psi cold they seem to handle but over 100psi and its trying to push the pump apart.

I have the same sort of thing going on, except mine is not newly rebuilt and has a gauge and filter.
Everything is fine: 80 psi at first, dropping to 60psi after a few miles. But, after about 10 miles at highway speed pressure starts going down. If I keep the revs up, it still manages 30 to 40psi, but it scares me.
Valvoline VR 20/50 oil. Iron pump, piston-type OPRV.
I'll clean the sludge trap this Winter.

If the oil is getting hot it may be worth putting an oil cooler on it which would keep the oil cooler and the pressure up better.
I'm very much an advocate for roller conversions and end feed, for such nice bikes. I notice Edward and Bella sitting on a nice A65. Newmoon isn't released out here yet but does anyone know if they use the BSA in the movie?

i have a pressure gauge.. i'll install it directly at the idiot switch junction just to be sure. i haven't installed an external filter, but will soon (i know, kinda silly not to do it during break-in if i'm going to). i run 20W/50 oil. 30 or 40 PSI sounds safe to me... 7 PSI (light still on) at 3000 RPM, not so much.

i was planning to test running pressures... i juts remember reading somewhere on here about PR valves not working properly with the wrong washer or something like that. ring a bell anyone?

Hi,



Ime, BSA publications were less-forthcoming about oil pressure than Triumph ones. Until someone expert comes along, from my experience of Triumph twin engines, 80psi cold, 60psi hot above 3,000rpm, 25psi hot idle; I'd allow the latter to be 50psi and 20psi respectively but not much less. Based on that, imho 30psi normal running pressure is too low.


You should find the thread is 1/8"NPS but keep an eye out for 1/8"NPT. When Triumph and BSA started fitting o.p. switches at the beginning of the '69 season, the taper-thread switch is what was used for the first few months; these bikes have been around for a long time and bits got swapped about.

Edit: Hmmm, I just read in the OPRV thread on the Triumph Board that the BSA OPRV is set to only 50psi.

Hth.

Regards,

Don't know if that 50psi is an exact setting or what one could expect under good conditions, it may be that hot at some rpm the valve isn't bypassing anymore. With an end feed conversion it usually is higher, having only two bearings to pressure feed, but is always temperature sensitive, and pressures 80C 60H and 30-40H at idle easy to get.

1. The OPRV should be sealed to the case with a very thin washer. Some people supply a very thick fiber washer for the OPRV. If you have a thick washer, toss it. I chamfer the cases and use a thin o-ring in the groove on the OPRV for a seal.

2. Many late engine have crap cavities for the switch. It is angle drilled into the main oil galley. Many (but not all) cases have very little "break through" into the oil galley. In effect, you are measuring oil pressure through an orifice. When you put oil through an orifice, you deal with pressure drop . I have measured as little as .015" break through. I don't know of an easy way to fix this issue. Even a gauge is going to read very low oil pressure with this type of cavity.

3. Make sure you have the right pressure switch. BSA used a lower setting switch than Triumph. The commonly available switch is Triumph.

4. If the engine actually has low oil pressure, pull the sump and see if you have shinies....

5. Did you install an SRM relief? IME, it is better made and works better than the stock BSA relief.

the OPRV is sealed with a thin washer.. there was a thicker one in the kit, but this information is what i thought i had remembered, and so i left the old one in there. i'll pull it off and inspect again.

i can't say for sure if i have the right switch, but it appears like the OEM unit in my '71 parts diagram. i should probably spring for the SRM product.

i pulled the sump plate when i did my first break-in oil change, and there were no unusual shinies... a little metallic color to the oil, which i'd expect with new bushings and rings.

Hi Paul,

I went through the things you are going through right now. I have the SRM OPR and a Lockhart Oil cooler with thermostat plus a Norton spin on Filter on the return line. Since then I ended up having the engine rebuilt and when the motor got hot the light would still come on.

I replaced the pressure warning switch with one from NAPA but I had to mount it on an extension as it interfered with the case. My switch goes on at 5 psi. I am running Spectro Golden 4 oil 20W50 with some Lucas Stabilizer (which thickens things up a bit). This keeps the light out.

When I rebuild the Firebird or the Star I will do the roller bearing conversion as the timing side bush can't be anything less than perfect which seems to be too much trouble in this day and age.

Paul:
FWIW loads of Brit cars used the same LOOKING oil switch, most but not all of them were stamped with psi in variuos places.They seem to vary from 7-12 psi, probably with everything in between.

gauge is the way to go if you can fit one.

can anyone tell me the correct length of the spring in the late (domed) OPRV? i swapped mine out for a spare (with no positive change) while inspecting mine, but can't find specs on it anywhere. my spring measures at 1.25" in length.

I do have a small oil cooler in circuit.
I have read in other posts that the cavity for the switch was not the best. I wonder how accurate my gauge is, being mounted to that orifice.

David,
"I wonder how accurate the guage is"? That's a good question. Generally the gauges made tday...even the cheap one's are fairly accurate...mayby not to a a couple psi, but within a range they are OK. What makes a guage inaccurate or more correctly misleading is if there is a lot of oil flow going to bypass it will create a pressure drop in the system especially in the area where the gauge/bypass is located. You could be getting misleading readings. I tested my 66 A65, which has no provision for measuring oil pressure. I made a test rig where I totally closed off the bypass and and measured my oil pressure. Believe it or not I had good oil pressure...about 18psi at hot idle and around 55psi at 3000 rpms, and it pegged my 0-60psi guage at any rpms beyond 3000. Of course when I took out my test setup and replaced it with the later OPRV, my system could have lower pressure at the bearings because of an improperly functioning OPVR or becuase of internal leaks or because of orifices so small that the pressure at the bearings cannot be maintained at a high level. A pressure relief valve is installed on most all engines for a couple of reasons (1) To prevent over pressuring the bearings. I have read that 60-80 psi is about the maximum allowable pressure for the early soft (copper/lead alloy) bearings. (2) the second reason is to limit pressure so that you are not wasting HP or wearing out your pump. Gear pumps if deadheaded can make very, very high pressures. Since most modern engines use gear pumps, pressure relief valves are a necessary part of the system and BSA's are supposed to relieve at around 50 psi. I am getting by with my original el-cheapo alloy pump. I would like to have a heavy duty billet type pump that is well torqued together and has the proper internal gear clearances and enough volume to always keep the BSA at optimal oil pressure. Plain bearing motors have been around for a hundred years and there are pumps and relief systems that are reliable in these motors for several hundred thousand. BSA recognizing this changed pumps and OPRV late in the game. If you are woried about your pressure, you can make a test rig to see what kind of pressure your pump makes out of the original OPRV with the little ball and spring. Other than that, upgrade to abetter pump , a better OPRV, and cross your fingers.

Mr Mike

mike,
if you make a test rig mounted at the OPRV orifice, won't this only tell you what pressure you have without any PRV at all? seems helpful to know your pump is working well, but still leaves the operation of the OPRV to be tested at the sending switch. still, knowing the pump is making adequate pressure is a good starting point.

Paul,
You hit the nail on the head. I know my pump makes adequate pressure...there's some comfort in that. I can't be absolutely sure that once I have the OPRV back in that I am making good pressure at the bushing and rods. But after doing the test, I quit worrying about it. Every year or so I perform the test again and so far it has shown good oil pressure. My rebuild only has about 8000 miles (I ride several bikes) on it but it sounds and runs the same as it did back when I rebuilt it.

I considered making an external relief directly to the tank with a guage plumbed into the cavity and the bypass loop down in the cavity closed. But I never bothered. You know about that old thing called a "Round Tuit".

Mr Mike

Its no use kidding yourself,guys. The gauge readings you are getting are as accurate as that gauge can be ,in any installation.
The gauge is on the pressure side of the OPRV.On the "dump" side of the OPRV the pressure is less,approaching zero.The pressure is high (or should be),anywhere on the pressure side of the OPRV.

As for the orifice size at the gauge fitting,it wouldn't matter if it was only 0.003" diameter .Once you've filled the cavity in the pipe and gauge (and this only takes a second or so),the reading is true.If you have a large enough oil leak in the pipe or gauge-head,then it will not become filled and you could get a reduced reading.

The whole plain bearing system only consumes about as much oil as you could pump with similar pressure through an orifice 1/32" diameter,exhausting to atmospheric pressure.
Check the OPRV spring and all clearances on the OPRV.

Hope this helps,I just don't want you barking up the wrong tree.
Pete.

Hey Pete,
No one is kidding themseves. There must have been 50 posts over the years that go like this: "I recently rebuilt my A65 bottom end and after a long ride I notice my oil pressure lite starts to flicker at idle. So I stuck a guage in there and I had 50 psi at startup but after about 10 miles the pressure dropped to 5 psi...should I keep riding it?" The system does not seem very robust based on all the chatter over the years and I guess every one wonders why. That is why I tested mine. If I had know the history of these bikes I would have drilled and tapped a port for a guage when I tore it down. Good oil pressure and clean oil is the lifeblood of a plain bearing motor. Even BSA made pump changes and relief valve changes in the later years so they knew something was not right. There is something that isn't quite right with the system and I guess we are spreculating to some degree on the cause(s).

Mr Mike

i've been unable to find any specs on this spring. i asked above and noone has replied... do you know what its proper length is? i can't tell how else you'd determine the proper function of the valve if not by reading oil pressure on the pressurized side or by determining that all components are within specs.

as soon as i get the chance, i'll try to do some pressure tests at the OPRV as well as at the switch orifice with the PRV installed. if i can get a decent reading, i may experiment with spring preload and see how it affects operating pressures.

Paul,
I understand your frustration. Perhaps you can stick a gauge in there and see what the maximum pressure is that you can make. If it is close to 50, leave it be.

Paul,

I've checked three different repair manuals including the original BSA Workshop manual for 1971 & later 650 models. They all state that the PRV is "self-contained and cannot be dismantled". They also don't list a free length for the spring like Triumph does so maybe the BSA PRV can't be disassembled. My 1971 Thunderbolt engine is dimantled and stored away so I can't get to the PRV at this time and can't remember if the above info is correct. I know there are discrepancies in some of the repair manuals so I don't always trust the info provided. I did find a spec sheet that I copied from an unk. source years ago that states that the spring length for the PRV that used the ball had a free length of .609" with a ball diameter of .3125".

It seems that once the oil gets hot, especially in OIF bikes that get hotter than dry frame bikes, the oil pressure goes down with multi-grade oil. Since I live in a moderate to hot climate, I've been considering a straight 50W to see hoe it works.

If you have already put an oil pressure gauge where the sending unit goes and getting only 5psi at crusing speed then you may have a leaking oil pump or your bearing clearences are suspect. The general rule of thumb for plain bearing motors is that you only need 10psi oil pressure for every 1000rpm. If you have anything close to that, you should be all right.
Ken

They usually state they are "self contained" because there are no internal parts available. You can still take it apart, inspect, and clean it. The spring on a ball type and piston type valve is very different. The ball type only has to lift off the seat to regulate, the piston type has to move the piston beyond the relief port. The piston type does not need a clean, smooth seat like the ball and the longer the piston, the less leakage before regulating.
Dry or OIF frame should not make any difference in the oil temperature. The dry frame holds a little more oil so it takes longer to heat up. It may dissipate heat a little better not being directly behind the motor.
I do not see any benefit of using a single grade oil. Once the motor heats up to operating temperature, the viscosity will be the same. The difference is when the motor is cold, single grade oil will generate very high pressure and could damage the pump, OPRV, or the bearings.

I don't think this is quite true. "Head Pressure Loss" through a pipe (or orifice, if it's sufficiently small, goes up inversely with the square of the diameter of the pipe or orifice through which it is flowing. The effect might not be noticeable going from a 1/4" to a 1/8", but I expect you'd see a BIG difference at something that's human hair sized?

Hydraulic engineers, front and center!

Lannis

The thing about a guage that I like is that once you know how your motor behaves eg how long it takes to heat up and pressure drop ect then you can pretty much spot it missbehaving realy fast off a guage.

I kind of use my guage as a comparitor rather than a strick measuring tool i look for consistency rather than readings, if you follow my meaning.

I dont look at it at idol after a run on the motorway....it only causes anxiety.

dont worry mine dose the same have run many thousands of miles like that at motorway pace 80 cold 50 norm motorway 50 to 20 use 50 monograde no oilfilter but an oil cooler

Lannis,

In a closed vessel, the size of the opening doesn't matter. The pressure is displaced equally through out the vessel. But, we are not dealing with a closed vessel. We are dealing with flowing oil in a dynamic system. Damn straight the size of the opening matters.

Some of the cases are drilled completely through into the the main oil galley. Those engines never seem to display "low oil pressure". Others barely bisect the main oil galley, they constantly have low oil pressure.

Add in using incorrect switches (very likely) and you can't get accurate readings. IMO, adding the switch cavity was one of the dumbest things BSA did.

They fixed that goofy angle drilling for the oil drain, which from your experience is problematic, increased pump size, improved the relief, and added a switch that may or may not cleanly read oil pressure. What a brilliant move.....

IMO, the best solution for Paul's problem is to remove the bulb from the light and ride the bike. For all this talk on the internet of "low oil pressure" it is amazing how many A65's continue to run. And run well. If there was such an epidemic of "low oil pressure" there would be damn few of these bikes still running and running well.

Paul,

Remove the switch and with a a light and possibly a thin piece of wire, probe the switch cavity and determine if it actually breaks cleanly into the main oil galley or merely made a glancing blow. Check your sump for shinies just to be sure.

And to answer your question about the spring length, the 70 manual lists 1.370". Make sure the washer under the dome nut is thin also. If that washer is too thick, it can affect your oil pressure.

great discussions, guys. rich- thanks for the spec. looks like mine is just a hair short, which could mean that it's fatigued a little. i'll look into the switch cavity as you suggest. i also have an oil cooler which i'll install soon. i was hesitant to do so just as the cold weather is setting in, but i'd rather run a little cool and have to use choke longer than overheat. i'll also run an external filter at the same time.

i'll note that though there are plenty of BSAs running around with these flickering oil pressure lights, there are also plenty- like mine when i got it- that had catastrophic failure from lack of oil past the timing side crank bushing. i know my clearances are good, i just want to make absolutely sure that a worn bush was the cause of previous poor oiling and not the other way around.

last night i got a new diagnostic condition... complete darkness. i was warming the bike up in the dark, and noticed the head tubes glowing dull red!!!! i killed it, cooled it off, but had no choice but to limp it to my shop which was luckily not too far away. it was pouring rain and i had to be somewhere.

anyway, i rode the whole way choked as much as possible to help cool the cylinders and it got there fine, oil pressure light staying off. took its temp as soon as i stopped, and it was 300F at exhaust side of the head. oil temps weren't too bad, at 125F or so. pulled the plugs and they looked sooty, which i would expect after choking it the whole ride. checked the timing and it was WAY off... after fixing this i loctited the screws again, but i'll be getting some studs and nuts for the plate soon so i can tighten them a little harder. i'm hoping the timing slipping accounts for my heat problem (measured much cooler after re-setting it), but i still worry. i suppose it would have totally failed if it had also had poor oil pressure.

side note: riding home, the engine performance seems a little worse. i'll double check the timing and reset the idle mixture screw, but i'm sure i did these right. could it have possibly been running better with the timing a little off? i know it should run best at the correct advance, but it makes me wonder if the center of the rotor could have slipped a little. it seems solid while i had it out.

Paul,
I have seen severely retarded timing make the pipes glow red. You are probably still burning fuel coming out the exhaust. Most of heat is likely in the pipes. You probably did no harm, but do get it timed correctly. I don't think that the slots in the plate would let you retard it that much unless you it was very much retarded to start with and then slipped further. Make sure you timing marks are correct. If not sure time it manually by setting the piston at about 3/8th" BTDC (I can't remember the exact number) and the cam at full advance when the points open.

Mr Mike

Okay, i don't want to hijack the thread, but its a related and apparently common story. I too have recently been thinking about this due to an orange light glowing from my headlight shell. I know i'd read about it before but couldn't find the old oil pressure threads either.

I restored a 1970 Lightning and have about 750 miles on the motor which was rebuilt by a reputable shop, 20/50 oil.

It was an unusually hot day (probably near 100) and with girl on back, motored up a steep, lengthy, twisty grade....2nd gear, probably around 3k revs. Once at the top, with the motor idling i noticed the oil pressure light was ON. I crapped my pants, then i turned off the engine. After freaking out for a bit, i began to remember previous posts about oil pressure and determined that the oil had become less viscous (thinner) with higher temp and required more turns of the oil pump to satisfy the oil pressure switch. Restarting the bike, the pressure light would go out with a sustained rev above idle, check. So i'm thinking at that point, do i let it cool down until the light remains out at idle? Or do i cruise downhill and keep the revs up until the bike cools down? I guess i did a little of both and got back home without further issue.

Question that has remained is: Did the engine suffer any damage from low oil pressure? I changed the oil and it looked like there were fine shinys in it. Still breaking engine in? Maybe. Excessive wear? Maybe. I don't know, but I'm not inclined to open it up to find out.

From reading, i don't know what my actual engine oil pressure is unless i install a gauge. And my oil pressure switch may be giving hokey readings due to poorly machined galleys. However, if the oil light comes on due to hot, thin oil, is the engine suffering from low oil pressure/thin oil conditions??

Insight appreciated, Greg

Greg,
This is one of the most often debated topics on the BSA forum...particularly A50's and A65's and many threads start just like your story.. Some say it really isn't low oil pressure...its the sending unit. Some say it is the fit of the OPRV in the oil "galleries" (not "galleys"). Some say their bikes run fine and long lives on low oil pressure. Others say to disconnect the light so it doesn't drive you crazy. Others give up and go to an end feed pressure system.

Here's my 2 cents: (1) I would not ignore an oil pressure lite that stays on at idle ...say 1000 rpms. The lite comes on a 7 psi which means your sending unit is either bad you have low oil pressure....less than 7 psi. Sending units are fairly reliable devices. (2) Plain bearing motors need adequate oil pressure to provide lubrication. 10 psi for each 1000 rpms is a rule of thumb. So if you had 10 psi at idle the light shouldn't even flicker. (3) Modern engines run down the highway at 55-60 psi at 2000-2500 rpms and have 20-25 psi at idle.
Don't stick you head in the sand and ignore it. Put a gauge on it and see what you have. If you don't have a place for a gauge you can make a test set up out of an old OPRV. If you don't have decent oil pressure try and figure out why. It might be the relief cavity or the OPRV but that's a stretch for me. It might be excessive clearance in the bearings, or a loose pump or a bad pump. I had to test mine for peace of mind.

Now to answer your question: I seriously doubt that you did any terminal damage in a short run up the hill in 2nd. But running low oil pressure over long periods of time wears out the engine prematurely. BSA would not have changed pumps, changed the OPRV and added a warning light if they were not aware of the problems they were having with low oil pressure. If you test it and have normal oil pressure....ride it. If you don't have decent pressure, it's time to check things out, but i wouldn't tear into it without a test with a gauge.

End of 2 cents. Others will have different views but that's what these forums are all about.

Mr Mike

mr mike,

without having specific knowledge of these engines (that's why i come here), i tend to agree with you completely. there has obviously been a historic problem with oil pressure in A65s, evidenced not only anecdotally but in the changes BSA made that you noted. any plain bearing engine needs adequate oil pressure to keep the metal surfaces from getting too intimate. i don't necessarily distrust the advice of people on here who have played with these engines for much longer than i (again, that's why i come here), but the skeptic in me does want to know first-hand what's going on.

in regards to pressure at the switch: though the pressurized oil system may not be totally closed (it does have an "out"), my layman's physics instinct tells me that the pressure must be constant behind that "out", regardless of the size of the orifice. i could be wrong though... i know physicists i can consult. if i can test pressure from the pump to be adequate, it only seems a matter of ensuring that the OPRV isn't dumping too much of that pressure. i know my clearances are good.

EDIT: after thinking about it, pressure between an "entrance" and an "exit" seems like they would be regulated by the pressure coming in and the orifice it exits... any point between that has no exit- say the switch housing- regardless of the size of the orifice would see the pressure between point A and B regardless of how it changes. i could be wrong, but the light will still make me nervous until i understand why it's doing what it's doing.

Hey Paul,
I think you understand it as I do. For example, the cavity for the pressure reading device (gauge or indicator lite) is supposed to be in a deadheaded cavity. In other words if the pressure developed by the pump in the galleries is say 30 psi, then a guage in the deadheaded cavity should also read 30psi UNLESS, there is some leakage out of the cavity. That is a possiblity and may well be true in some cases. The drilling into the cavity may not be good and the leakage past the threads may contribute to a measurable pressure drop on bikes fitted with a pressure indicator port.

If you have an indicater lite that stays on, make a test setup and see what you really have. It is really pretty simple to do. My 66 has no drilling for an indicator lite, so I tested with the pressure relief closed off and was happy with the result...at least content that the pump made pressure and the clearances (.0015")on my bearings were right. I reinstalled a late model pressure relief replacing the original ball and spring unit so that I did not overpressure the pump and bearings (especially when cold and my pump pegged my 0-60 gauge at 1500 rpms when cold).

My feeling is that the system is not as robust as it should be. The B25 unit single and the A50/65's were all problematic for BSA and they had similar systems. Some owners get long life out of there BSA's but many do not and everything points a reasonable person to suspect oil pressure. So my advice is to put in the best pump you can find, use the later style prsssure relief and install a gauge if you have a port, and put a good filter system on. If I ever have to rebuild my A65 again, I will drill and tap it for a pressure reading port.

Mr Mike

go put that in my "A65 engine rebuild catch-all" thread! sure could be useful to the next guy...

Hi,


Just a thought but, if your engine already has a port for the o.p. switch, why not attach the line for a gauge there as well?

Fwiw, that's what I've done on my Triumph T100. The readily-available switches have a 1/4" length of 1/2" o.d. just behind the hex. of the switch. I turned this down to the thread o.d. (0.405") then cross-drilled and relieved it like a banjo bolt about 3/16" down from the hex. (a Goodridge banjo with a copper washer each side is about 3/8" thick overall). So that bike still has the standard warning light, and a gauge; fwiw, I've a Triples Rule clocks mounting bracket, that the '71 clocks and rubber cups drop straight into.

Hth.

Regards,

Stuart,
My 66 A65 does not have a warning light port to work with. That didn't come till 69 I believe. I felt like I could find a safe place to drill and tap the pressure gallery, but only if I had the cases apart so i can see where I would be drilling.

Mr Mike

when i bought the bike, gary (was a member here) had plumbed up a t-fitting for the original switch and a compression fitting going to a gauge at the bars. i would have re-installed it, but the plastic line was crap. my concern though, was that before the light the gauge showed just what the light warned. now without the gauge the light still does the same. that either means that both are getting a false reading, or that my switch has now become faulty after the rebuild.

the light came on again today and would go off unless i really revved it up. i need to sort this out for some peace of mind.

Hey Paul
I had the same dilemma and using a spare OPRV, I soldered up the bypass holes and tapped a hole for a gauge in the hex nut. This in effect seals the cavity (no relief). This should allow you to read pressure at the bearings eliminating a faulty sending unit (which I doubt)or a leaking OPRV. See what it is. Do not overrev the engine if the pressure is too high as you have no relief. At idle you should not have more than 50 to 60 psi. Let it warm up real good...in fact you might take it on a good test ride to get it hot first ....and then do the test. I used an old ball type OPRV. If you have unsatisfactory oil pressure check out your pump installation and the pump itself. Your's is a 71 and should have the cast pump..an improvvment over the alloy ones.

Since I have no port for a gauge or sending unit, I seriusly considered installing an external relief going directly to the tank with a tee in my gauge line. After several tests with good oil pressure I scrapped the idea.

Good Luck, Mr Mike

Mike sez:

"Your's is a 71 and should have the cast pump..an improvvment over the alloy ones."

The cast iron pump did not start with the the 71 model year. The cast iron pump was a running change that may have occurred in 71 model year. Other than body material and some passageway changes, the cast iron pump uses exactly the same width & tooth count gears as the late alloy pumps. You end up with the same flow.

my pump is alloy, sadly enough. if only it had been born a few months later...

i have little experience with the BSA OPRVs, but i have squeezed high flow out of the oil pump on my Honda ('76 cb550, simply by shim preloading the spring in the PRV to blow off at a much higher point. i had almost the same type PSI in that engine once warm, and being a very hot-rodded engine, i needed the higher pressure.

the thing that makes me question a faulty PRV is that unless i'm thinking about this wrong, it should actually stop relieving pressure when the oil gets hot and thin. on the other hand, raising the pressure relief point did fix the same problem in my Honda, however counter-intuitive.

i have part of the day off tomorrow and will try to do some diagnosing.

Hey Paul,
The OPRV should not open below say 50 psi(if that is where it is calibrated at). Pressure is pressure whether the the oil is cold and thick or hot and warm. If the pressure relief is vibrating open or otherwise relieving pressure before say 50 psi then that is a problem. That is why I am suggesting a test where you block off any possiblity of return and measure the pressure at different temps and rpms. Then put the OPRV back in and do the same test reading the pressure with a gauge. If the pressure is a lot less than the test conditions, you likely have a problem in the relief valve area. I can't do that on my 66 bike because I don't have the extra port to read the pressure so I just must assume that the OPRV is working OK.

Rich, I like cast iron because of it's rigidity compared to alloy. I used a lot of fluid metering gear pumps in industry and they were billet style pumps whose plates that were thru bolted, torqued with pinned sandwiching the gears. The ran 24/7 for years. When we rebuilt them it generally took just a little lapping to get them back in the game. I understand Ed V has some bodies that reuse the existing gears. Don't know if they are billet types. I just don't know much about them. I just dislike the alloy pump's flimsy nature. It binds if you torque it too much. It's alignment is suspect and that is what is running in my bike.

Mr Mike

Mike

I think you misunderstood my reply. You had commented a 71 had a cast iron oil pump. My reply was to point out that a 71 may or may not have a cast iron and to make sure Paul knows that other than body material, there is no difference in capability between the 2.

Last I knew, Ed didn't have any pump bodies. They were listed as not available on his website. That may have changed recently.

Hey Rich,
I actually understood your reply which concurs with Steve Wilson's info. I was just running off at the mouth....er keyboard adding another 2 cents about pumps in general. I checked Ed's site and he is still out of pump bodies. Have you ever seen one of his?

Mr Mike

Mike

No I haven't seen one of Ed's pump bodies.

I am not convinced the alloy body is the entire reason for tight pumps. I have a cast iron pump that is also tight. It seems to me to be more of an issue of BSA not very carefully matching gear sets prior to assembly. I have also not seen evidence of wear suggesting the body itself was warped.

With the low volumes and pressures the pump runs at, it is well within the capabilities of material.

In industry we never mixed and matched gear sets and bodies. The were all wired together when disassembled so as not to get mixed up. I feel like the cast pumps would provide more rigidity that the alloy and might be less susceptible to binding but I don't have a whole lot of experience with them.

Mr Mike

ok, i finally have a little data to work with.

i re-installed the pressure gauge at the switch port (keeping the switch), and got about 35 PSI at cold kick over. revving it up, it only goes to 40 PSI or so, and by the time it was warmed up and i was home, it was reading 7 PSI at idle. most of the ride home was at 40 PSI, but it was a little hard to read in the dark on the freeway in the rain. i didn't have a chance to really warm it up to the condition that causes the light to stay on even above an idle because it was pouring rain and my boots were leaking a little bit.

the pressure gauge is mounted up at the bars, so i suspect accurate reading with the line having so much air in it to compress as the pressure rises. i do believe i really need to test that pump now though.

update: starting it totally cold (after resting overnight), the pressure got up to about 50 PSI when riding.

Hi Paul,


Incorrect assumption - the line won't have air in it. If you don't believe me, undo the connection between the line and the gauge - bet it leaks oil straight away.

Hth.

Regards,

you're right that it'll leak oil because there is oil in the bottom, but the line is clear plastic and i can assure you there is air in it. you can actually watch the oil rise in the line upon startup. i should bleed the line.

Paul...."the pressure gauge is mounted up at the bars, so i suspect accurate reading with the line having so much air in it to compress as the pressure rises"

The air will still compress to the same PSI as the oil so shouldnt affect your reading. (might make the needle bounce about a bit though)

I have my gauge mounted between the tach and speedo on an adaptor plate and have that clear hard type pastic tube which is about 18" too long (i just pulled it out of a car and was to lazy to cut the pipe so just kind of coiled it up...must fix that sometime)

I suspect the air in the line is just becasue of a "marginal" line/gauge fitting.

Any how I can see about 4-6 inches of air in the line below the oil gauge, and some air locks in the "coil" as well doesnt seem to affect readings....Get 60psi on cold start 40 psi on cold/warming up idol, 20-30 heated up on motorway speed drops down to nearly zero (maybee 5-6psi) at HOT idol.

Its remained consistant for the past 4 years so isnt getting worse.

Hi Paul,


Uh-uh, I meant the connection of the line at the gauge. However, ...


Summat wrong with your gauge/set-up then? I've had o.p. gauges on two triples for something like 15 years, triples have been fitted with o.p. gauges as a regular thing since the mid-1980's and my T100 has a gauge. I've always assumed that a gauge bleeds off any air/gas automatically because, in all that time, I've never known any owner of a triple with a gauge ever worry about measuring gas pressure instead of liquid pressure.

Hth.

Regards,

Time for a hydrostatics expert to weigh in; I know we have one or two hanging about.

Say there are two identical lines connected to two identical gauges, with 50 PSI on the sensor end of the line.

One line is completely full of oil. One line is half-full of oil, and the rest of the line up to the gauge is full of air.

I believe the gauge will still read 50 PSI. The air in the line HAS to be at 50 PSI (subject to "head" losses in the line, which is true for both air and oil and should cancel out.)

Won't the gauge read the same in both cases?

Lannis

The difference is pressure be (density*gravity*height). Height is the difference in height between the partial full line and the full one.
The air above the oil would not make a noticeable difference in the reading. The air will stay there until the pressure causes the air to dissolve into the oil or the gauge is left below the source long enough for the air to creep out.

Methinks 50 psi is 50psi is 50 psi....that's what my Physics teacher told me. There might be a little time delay as the air compresses but not noticeable and if there is no flow (No leaks) there are no head losses and both gauges read 50psi It's a static system. It's like the home presure cooker at 10 psig. The presure is the same under the water as in the vapor.

A mechanical engineer who took fluid dynamics can give us something more official sounding.


Mr Mike

I don't think we need an ME to answer this one, nor an EE who studied a little physics.

Air trapped in an oil pressure gauge line will NOT change the reading.
A small diameter OPG line will NOT change the reading.

A small diameter line or orfice restricts flow rate, but not pressure.


now:
""last night i got a new diagnostic condition... complete darkness. i was warming the bike up in the dark, and noticed the head tubes glowing dull red!!!! i killed it, cooled it off, but had no choice but to limp it to my shop which was luckily not too far away. it was pouring rain and i had to be somewhere.
""anyway, i rode the whole way choked as much as possible to help cool the cylinders and it got there fine, oil pressure light staying off. took its temp as soon as i stopped, and it was 300F at exhaust side of the head. oil temps weren't too bad, at 125F or so. pulled the plugs and they looked sooty, which i would expect after choking it the whole ride."" Paul

Paul
There is no relationship between an oil cooler and red exhaust pipes.
Oil at 125F is stone cold and a cooler will not be good.
IMHO You need to let the oil get much hotter than that to drive moisture out of the engine and thin out to reach all lubrication points.

As for the minimum safe pressure for an A65, unfortunately I have no useful knowledge , let's get some more opinions. Where are those NOPG guys?

hey guys. first off, i agree that the gauge will ready properly regardless of the air in the line, but the air compresses at a different rate than the oil, which accounts for the lag in reading at the gauge. when i start it up, it takes a few seconds to reach the operating PSI.

SBoyd- i would expect that an oil cooler would help in warmer temperatures when the bike gets nice and hot and the oil is after all the medium cooling the engine. i'm running by bike in 45-55F temps right now.. i don't think i said that an oil cooler would have anything to do with the red hot headers, but i'll look back. i'm not sure exactly what you were referring to, but you quoted the bit where i was referring to keeping the bike cooler via choking the intake. fuel and cool air thought the intake valve does cool the intake valve and cylinder, and though it may not make for the best running condition, a rich mixture can keep an engine from overheating in a pinch.

in any case, i'm still getting next to no oil pressure at the gauge at warm idle, which worries me despite all of the comforting advice i've received. my sage machinist to whom i normally turn with such quandries just died a couple weeks ago, so i'll have to keep searching for answers. thanks to all for the help.

SBoyd sez:

"A small diameter line or orfice restricts flow rate, but not pressure."

An orifice in a "dynamic" system does in fact cause pressure drop. It is Hydraulics 101. And well understood and frequently used in hdyraulics for measuring and control.

As long as oil is flowing in the engine oil galleys, any significant restriction between the main galley and the gauge will cause a pressure drop.

BTW I am the founder of the NOPG Society. An oil pressure gauge is the worst device ever offered for installation on a BSA unit twin. Unless you can directly read the pressure at the base of the OPRV, which requires welding and machining to fit.

Paul,

Like many late unit twin owners who have fitted gauges and switches of unknown trip points, you are dealing with readings that will cause ulcers. Or cause you to go postal. Again, does the engine make noises that it is in distress? Does the engine generate shiny bits that are not a good thing? Have you switched to an SRM OPRV?

If the engine is not giving any signs of distress, sort your timing/carbs, break it in, then ride it like you stole it. A65's actually seem to like that treatment. At least mine do, Alex's do, Bonzo's do, Lannis' do, etc.......

Paul,
I don't know how to do that quote thing...but is this your quote that is in Sboyd's post?

"last night i got a new diagnostic condition... complete darkness. i was warming the bike up in the dark, and noticed the head tubes glowing dull red!!!! i killed it, cooled it off, but had no choice but to limp it to my shop which was luckily not too far away. it was pouring rain and i had to be somewhere.
""anyway, i rode the whole way choked as much as possible to help cool the cylinders and it got there fine, oil pressure light staying off. took its temp as soon as i stopped, and it was 300F at exhaust side of the head. oil temps weren't too bad, at 125F or so. pulled the plugs and they looked sooty, which i would expect after choking it the whole ride."" Paul "

Ths condition described sounds like severely retarded timing to me..... If the pipes close to the head were glowing red!!!

On the oil pressure...I'm in a different camp than others. I believe that these bikes ought to have in the neighborhood of 10psi/1000rpms. Check the machinery handbook. Whether that is consistently possible with todays parts and BSA's design I dunno. If they run with real low pressure I believe you are trading in long life. It probably won't go "kerblam" on you but it won't last like it should. I will admit that early cars (40ties and 50ties)didn't have as high oil pressure as cars do today, but the race guys and hotrodders of the period always put on gauges and had good aftermarket oil pumps on their stuff. As far as gauges, I'll wish I had one. If BSA put them on (like they should have) they probably wouldn't have sold too many bikes. Even the early aircooled VW's has warning lights and they work. I have a real good story on a VW oil pressure for another day.

Good Luck and stick with it. The bikes after 45 years are still a blast.

Mr Mike

My 2 cents.

Well I know what you guys are feeling. The insecurity of the oil pressure gage and light. It's like a that naggin' little voice in the back of your head that you have been trying not to listen to all these years. So if your are really worried that the oil pump is not putting out enough volume to keep the pressure up, then get the roller bearing conversion and have your pump supply just the big end bearings. And be happy. (That's what I intend to do).

BUT>>>

I know what a BSA sounds like when it doesn't have enough oil pressure. It is a really loud GaWD awful racket that another biker can hear from 12 feet away while riding. And I'm sure you guys don't have this because if you heard this cacophony of banging and chain knocking you would know that you have not got enough oil pressure. If I thrash the Firebird, the oil pressure light is full on at idle. But the motor sit there and purrs. It is not making sounds like it is coming apart. And there are no shineys in the oil.

What I would like to know is what Ger heard that caused him to tear down his engine (and discover all that damage).

Hello Ger? Maybe I'm wrong about all of this....

i hear ya Semper. the probem is, i don't know what normal clatter is for this engine... the only other pushrod engined bike i've owned was a '71 bonnie, and that was brief. i'm used to the cam chain rattle of 70's Honda fours. sure, i know rod knock or metal on metal when i hear it, but i' m still constantly listening to the motor and wondering if the sounds have changed.

after all, this engine was destroyed when i got it due to lack of oil pressure... i'd consider that reason enough to worry.

Paul...
"fuel and cool air thought the intake valve does cool the intake valve and cylinder, and though it may not make for the best running condition, a rich mixture can keep an engine from overheating in a pinch".

Your right about that for sure!....try running a motor way too lean and it will overheat big time, stands to reason that over rich (choke on) will be cooler due to the cooling effect of evaporating fuel, burning at lower temp ect.

I recon you need to listen to a few A65's running....you may not be comparing apples with apples. A65's do make a bit of a clatter compared with modern sewing machines on wheels. Normal "din" for an A65 isnt realy something easily described on a message board.


RichB....
" An oil pressure gauge is the worst device ever offered for installation on a BSA unit twin."

I guess that depends on what you use the gauge for. If you use it (as I do) to simply monitor for DRAMATIC changes like suddenly drops to zero while your riding along , it could tell you opv jammed, oil lines fallen off, pump is having a holiday, pump gasket has blown ect. I sure cant see how that is a bad thing. You will pick up a sudden drop in op much quicker with a gauge than waiting for the motor to let you know by exploding.

If however you use the guage as an "anxiety enhancer" I take your point.

today i flogged the [***] out of it up on my local twisty, and i can't say i'm much more comforted. on one hand, i rode for a good hour at high RPMs, but on the other, the indicated oil pressure- both at the gauge and the switch- read ZERO oil pressure through almost all but fairly high revs.

NOW...if i truly had no oil pressure at all, i'd have a dead engine right now, but i can't find a reasonable explanation for why the gauge reads 50 PSI cold, which is where the OPRv supposedly releases excess pressure, but is supposedly inaccurate once warm. ??? during this hard ride, the air in the pressure gauge line was visible, which means that there wasn't even enough pressure to compress the air and give an accurate reading. i will attempt to bleed the lines tomorrow, but with all due respect: i can't believe the folks that tell me to ignore the symptoms and just ride it. for those folks: will you back it up if the engine fails and i'm in search of something MORE than .060" over pistons, .030" under big ends, and .050" under main bush? all information tells me that i have poor oil pressure and that i'm lucky that it has done its job so far.

the engine was obviously less that totally happy under these conditions, but didn't give up the ghost.

Paul,
I only have one last ditch suggestion. Remove the OPRV and rig it so it can't bypass. A short piece of bolt instead of the spring and see if you have any pressure. Just leave the gauge abd eliminate that light if you have them both fitted. If you don't make pressure you need to visit that pump and its supply. If you have a filter it should be on the return side. I can't recall what work you did with the pump, but being a 71 it should have the bigger gears and may be cast iron.

You are getting some oil pressure or the motor would be finished if you flogged it real hard.

Mr Mike

Paul
Mr Mike has a good idea.
I had a similar problem on a Triumph and got this very idea from someone on this board and sure enough the pressure skyrocketed and the OPRV turned out to be the problem.
The length of the piece that you put in place of the spring needs to be just right.
On the BSA I'm not so optimistic, but I think it should be tried.
Good luck
>>sb

paul,
You'll figure out how to get the bolt the right length. That was my first method to test pressure because in my 66 A65L they have no port for a gauge. Later I soldered up the holes in one of the early OPRV's and made a test setup that I can check my pressure with from time to time. I was pleasantly surprised that I had decent pressure and I didn't do anything special with my early pump except put it together carefully. My bearings were all clearanced at .0015. Filter is on return side.

Good luck Paul. Keep us informed.

Mr Mike

"I can't find a reasonable explanation for why the gauge reads 50 PSI cold, which is where the OPRv supposedly releases excess pressure, but is supposedly inaccurate once warm. ???"
It doesn't seem to work the way you think, the OPRV may bypass at a particular pressure say 50psi, that's when it opens we think, however when its cold and open its usually got more than 50psi behind it because of the limitations of bypass flow and or thickness of cold oil. To get a normal hot engine pressure of 50 or 60psi means you will have 80psi or so cold everything being normal. I used to run higher than that looking for 75-80psi hot but that means 100+ when cold and perhaps over stressing the pump, which can spring it in the middle and spray oil out there.
Myself I would stretch the spring for 75-80psi cold and see what you have when it's hot. I'd do that before I'd lock the relief all together seeing it would have a H/volume pump.
Also being like a member of the oil pressure gauge society, I had an oil pressure gauge in a '94 Honda VFR 750 I had, it had very little pressure at idle when hot and the gauge almost worked as a rev counter, I think it had over 80psi at 10,000, the idea that the bypass valve maintained it at a constant pressure wasn't very true, it no doubt stopped it skyrocketing when cold but that was about it.
Modern cars seem to have smaller and smaller oil pickup gauzes we had a mitsubishi V6 with the oil light coming on all the time, at work and put a gauge into it-yep no pressure, so pulled the sump and declogged the pickup, what was interesting was 150psi, quized the mitsubishi guys and they said yea they run pretty high? So the point I'm trying to get at is the pressure bypass valve is limited in its control with all the variables they work under. It's not possible to make one give only 50psi cold and then 50psi hot as well, the hot pressure is more important, if you cannot adjust the relief to get most of it (50psi) at 3-4,000 it's probably dumping or bypassing oil somewhere.

""Myself I would stretch the spring for 75-80psi cold and see what you have when it's hot. I'd do that before I'd lock the relief all together"" Mark

Mark and Paul
This is for a test.
This is not a recommendation to ride the bike for any duration this way.
The point is to totally RULE OUT the OPRV and see what pressure can be made, hot and cold.

Mark's point is valid, but IMHO as step two.

IF the gauge SHOULD shoot up to 100 on startup, the engine should be shut off right then and the cheers begin.
If no gain is made, I guess the OPRV can be ruled out as part of the problem.

If any gain is made, spring stretching and substitution would be next.

>>sb

"Mark and Paul
This is for a test.
This is not a recommendation to ride the bike for any duration this way.
The point is to totally RULE OUT the OPRV and see what pressure can be made, hot and cold."
Yea I know, its likely worth trying I'm not against that, its just you don't want to see the needle doing laps of the gauge like when I put a H/volume pump in a rebuilt chrysler s/block with the relief valve spring jacked up on a nut I put in there for a bit of extra pressure :(:( I was young!!!, it blew the filter off, I was under the bonnet and my Dad was in the car when we started it, conversation went like this; Has it got pressure Dad?.....Dad??......Oh..It's just going round and round?? Then we had the oil thing happening Haha.
I've been thinking about it a bit and the fact that My A65 when its cold at 1,000rpm can have 60 or so psi yet when its hot in summer 20psi or very hot maybe 15 or 10 even, how much heat and oil thickness effects pressure, thats a massive variation and indicates how much faster the oil can get away when hot.

i'll try to rig up a pressure gauge at the OPRV over the weekend, or at least test it where the gauge is with the OPRV locked off. perhaps the OPRV is leaky and allowing hot low-viscosity oil to leak past the bypass piston even when not technically doing so? despite the apparently simple operation of the PRV (relieves excess pressure at 50 PSI regardless of oil viscosity), i think it is a little more complex than it seems. my Honda that i mentioned is a perfect example. i had almost the exact same conditions until i installed a stiffer spring in the PRV. now i get 70 PSI at cold startup and anything over idle, and 30 PSI at hot idle. on that engine i had ZERO indicated pressure warm, with the gauge installed directly at the pump.


i don't think i mentioned: i inspected the oil pump before re-installing it, and could find nothing noticeably wrong. the mating face was flat, and the gears looked healthy.

The std take off for the gauge is fine I endfeed my crank from that hole, its easy to stretch the spring by forcing the shaft of a small screwdriver between the coils, just do both sides or it will curve, and you can adj the pressure by just taking the cap off and spring out. If you lengthen it too much squashing it in a vice a bit will shorten it again.

Hey Paul,
What your are doing is simple to do and may eliminate a variable or possibly give you some more information. When I tested mine that way I pegged my 0-60 psi gauge immediately at anything over idle. As the oil heated up my idle pressure dropped till it seemed to stay at about 17-18 psi at idle and would be at 50 psi at 3500 rpms. I was satisfied, but it is entirely possible that after a long hard ride on a summer day that my pressure might be less. At this point I have to trust the system is ok for my needs. And to be honest, when I put the pressure relief back in I might get something different as I have no way to measure it without a port on my cases. I just believe that the BSA lubrication system was marginal from day one and that is what makes the endfeed so attractive. All the plain bearing motors of that period B25, A65, A50 seem to generate lots of complaints that point to marginal lubrication. Keep us informed and good luck.

Mr Mike

Mark sez:

"The std take off for the gauge is fine I endfeed my crank from that hole"

Some are fine. Some are not. I can't get pictures that show anything worthwhile, but I have 2 late cases that have virtually NO opening between the switch hole and main oil galley. The worst will barely allow a .015" wire through. But I have also seen late cases that switch cavity fully intercepts the galley. Would a .015" opening do your engine any good? I seriously doubt it.

I know for a fact that set of cases would always show low oil pressure once the engine was warm. And I ran the snot out of that engine, once the switch was disconnected. And that engine never once let me down due to an oiling problem. It just eventually got retired. And was tired

Paul need to: 1. Quit screwing around with a likely worn/scored/tired original OPRV and install an SRM OPRV. 2. Check his switch cavity. Little tough to do on an assembled bike, but possible. A light and some drill bits will tell him whether hsi cavity sideswipes teh galley or fully breaks into it.

i finally had some time to play with this today, so i did some tests.

first, i removed the spring from the PRV, and replaced it with a solid piece of steel round stock, shutting the relief off completely. kicked it over, and it pegged the pressure gauge. ok, the pump seems to do well cold.

then, i preloaded the spring about 1/4" and started it again. this time, the pressure was at about 80 PSI at idle, and would still go a bit higher if i revved it. i pulled the oil drain plug (was due for another post-break-in oil change anyway- no shiny bits, and the oil looked pretty clean still), and shortened the preload a bit while waiting for the oil to drain.

upon start up, i had 70 PSI at the gauge. got it nice and warm, rode it around a bit, and... the pressure dropped back down to zero at idle.

since i know my crank and rod clearances to be good, all i can think is that when the oil is getting hot enough, it is either creeping past the OPRV piston (which feels pretty snug in its bore) or there is another point of escape for the oil to cause the pressure drop. if someone can explain the physical reason why the gauge or location of the gauge would suddenly become faulty only when hot, please do.

i don't know what to test next without beginning to give a lot of money to SRM.

How was the pressure at 3-4000RPM when hot? Obviously oil temp is having a big effect. If the motor is new it could be running a little hotter than it might when run in more. Points of oil escape can be the 3 bearings, the bush being a little unconventional and less easy to check clearance when doing, cannot plasty gage.
But also the centre of the pump, if distorted or has loose bolts, as Rich points out thick washer on OPRV.

Paul,
A couple questions? (1) Did you put the piece of metal rod back in when the motor was hot to see if you had any pressure? Probably wouldn't change anything but I am just curious. I'll try testing my pressure again cause you got me thinking. (2) The first time I had a bushing bored the machinist missed the mark. When I got home it felt like the fit was too loose I brought it back and had him remeasure my crank with a micrometer and the bush with a dial bore gauge with me standing there. I was right and he redid the job at his cost. He openly acknowledged that it was his mistake. Are you confident that your bush has about .0015" (or close to it) clearance? (3) Is your idle real low? I used to set my ilde as low as I could get it but now set it at 1000-1200 rpms to make sure I have better oil pressure. If you can get 7-10 psi at idle and 30-40psi going down the road I would ride it. It isn't optimal by today's standards but should keep you riding.

Good Luck,

Mr Mike

Paul,
I've been reading all the comments pertaining to your problem and it seems that whatever you try leaves you with the same result. I know it can be very frustrating. I've been thinking about this for sometime and would like to make a few comments that may help you figure this problem out.

You advised that you rebuilt the motor. I assume that you had a machinist do the crank & rod journals. It sounds like you currently have .040" over pistons, ,020" under rod journals and a .040" under bush journal. I also assume that you actually put the motor together after the machine work was done. You advised that all the clearences were good but didn't state what they are. Did you actually check all the clearences when you put the motor back together or did you rely on what the machinist told you? Did you have .0015" end float on the crank and .0015" on the rod & bush clearences? As the clearences become greater than that on a BSA, your are going to have lower & lower oil pressure as the parts wear, even if your oil pump & OPV are perfect.

Did you use good quality rod bearings or Tiawanese copies?

You advised that at one time you got 7 psi at idle & 40psi while riding. Then you advised that you got up to 50psi while riding. Then you advised that you "flogged the [***] out of it and rode it for a good hour & both gauge & switch read ZERO oil pressure through almost all but fairly high rev's". You then advised that you shimmed the OPV, got 70 psi at idle and rode around and then got zero psi at idle but you didn't advise what oil pressure you were getting while riding.

If you "flogged the [***] out of it & rode for a hour with no oil pressure then the engine would be toast or you have a bad oil pressure gauge. If I were you, I would invest in a good liquid filled oil pressure gauge that goes to at least 60psi. Get a piece of 1/8" threaded pipe x 1 1/2" & a double ended female coupler to attach the pressure gauge so you can see it while riding. Instead of bending the OPV spring, you can shim it between the spring & plunger using 8mm flat washers or 1/4" AN type washers and get whatever release pressure you want.

I suspect that the gauge you are using my not be all that accurate, is it a 45 or more like a 320 degree sweep? I suspect that most of these gauges are probably more accurate on the higher end than on the lower end.

I don't think that the idle pressure is as important as yor crusing pressure. As long as you are getting approx. 10psi per 1000rpm, you should be fine. If you still don't get close to that while crusing, after shimming the OPV then you have either a clearence problem or an oil pump problem.

I hope I didn't come off as condesending in anyway, just trying to help out as best I could.
Best of Luck,
Ken

sorry, i try to include as much information as possible, but it's easy to miss some. at night, it is difficult to read the gauge while riding home. also, i don't have a tach, so telling you where 3000 RPM is will be a guess, but i'd guess 15 PSI.

1) yes, i did put the piece back in, and it had no noticeable effect. zero oil pressure at idle hot.

2) i really trust(ed.. he died a couple weeks ago) my machinist, and he did lots of these engines through the years. he knew the proper clearances without me even bringing the specs in. in any case, i know for a fact that the crank bush was set at .0015" clearance, as i double checked with a dial gauge once installed. i trust that the rod bearings were proper, but didn't verify myself. the guy that did them has done it for years and years and is an old man.

3) when i checked my dwell (what should it be, by the way? i think it was around 35...), the idle was right at 1000 RPM. again, i don't have a tach so it's a guess. if someone has a cheap tach to sell me, please let me know.