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

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.