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That would great if I ever need another one.


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The company is Lee Company, 82 Pequot Park Rd, Westbrook CT 06498 (800 399-6281). The part number for a 50 psi relief valve is CCPI8010350S. Remember the key to this project is the elimination of the BSA OPRV and the leakage which causes the loss in pressure. The pumps, later ones or the early alloy pumps make enough volume and hence pressure but the pressure is lost to leakage leaving the bearings short changed for oil.

BTW this company uses BARs as a unit measure of pressure so you will have to have a conversion factor or table available to convert to PSI.

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I might modify a ball type, block the return and tap one in and run it somewhere else. And see what it does. Pressure drops on these with heat and part of that is natural but how much of that is going across a couple of threads. It has pressure behind it, it could easily go across, because threads do not seal. It could just go into the case, maybe at the timing bung, I have a spare.


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Mark,
I modified an early ball type when I first tried this project. Works fine. I believe a lot of the oil goes through those 2-3 threads rather than to the bearings. The rest of the oil goes thru the relief. The BSA ball type and piston type reliefs do not completely close until pressure drops below 10 psi. In my case it finally closed off at 7 psi. I actually carefully monitored the relief oil returning to the tank through an external hose so I knew exactly when the OPRV closed. This is the phenomena known as hysteresis which I briefly described in the write up. If i was doing it over I'd use the new OPRV that opened a t a lower pressure. This little OPRV is so small it restricts return flow even when it is wide open. I worked so good that I didn't mess with it any more. You just have to let the oil warm up a bit before revving the engine.

Hope this helps.

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Honestly, you guys have to do this to me now? Literally put oil in the a65t project a week and a half ago. Was leaking from the junction pipe fitting, so drained and x-ringed and replaced this week. Now this.
At this rate I'll never hear this thing rumble.
Also it seems anytime I can't figure out a thread from the BSW, BSF and bsc ranks on my machine it's some form of bsp that would be 7/8 14.

Not sure I want to drain the oil again for this procedure, but the motor's internals are an unknown. Was built by PO up to the primary chain, so not sure what oil pump is in there. He was working with a reputable mc mechanic on it but a Harley guy maybe not hip to British nuance or these oil pumps known issues


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Just measuring the thread on this old ball pressure release it's 22mm od near the hex and 21mm od on the part that should seal. No wonder it's not good. Obviously not the ball and spring. What if it's turned down on the thread end? It's 12.5mm id and it was straight. it's 18mm od where the holes are and could be stepped smaller and grooved for an o ring. and have a plug screwed in with a hole that it neatly fits in and seals with the o ring which could be in further or not as long as it was in. The plug just sealed in the bottom of the cavity? Then it works as std except for the thread leak.

Make it something like this:

https://www.ebay.com.au/itm/393025803148?hash=item5b8229d38c:g:Ib0AAOSwq-dfuRzW

Then have a sealed piece with suitable hole in below the std oil bypass hole.

DM could you make something like that that fixed this?

On the other hand I have an experiment to try. I put this thing into an old case, I wound it in just on the threads that need to seal. It wobbled and rattled on just those threads, even almost right in it was wobbly. So I shoved it in the lathe and turned the front off a bit. In hindsight I should have just ground a tool and put an O ring groove in that threaded section and the O ring would stay in winding it out.

Never the less I push it down and turn with a little grease, it's firm to turn by hand and I can feel it try to catch a bit at the hole but it keeps going and gets spanner tight right near the end. The O ring is still dragging on the thread. So wind it out and the O ring falls off the thing which becomes loose. But pulling the O ring out and it's undamaged.

So something to test on the Firebird and see what it does. What I do know is it will not be like before, when I decided to put the piston type in. I figure oil pressure will force the O ring against the shoulder and it will seal the thread. I just have to wind it in and tighten it and the O ring stays pushed against the shoulder. A groove for it may allow the gauze on the end to stay. It would be funny if it was this simple. I have a gauge so will be able to see what it's doing. Then I get it hot and see where it goes. I thought I might destroy the O ring but it seems fine. This will be interesting. And the old piston one may get a groove. It has no gauze already, why I used the ball one first till hot pressure was so bad.

[Linked Image from i.postimg.cc]

Maybe if this helps pressure, the bush may be a better lasting proposition. And the big fault with the oiling on these the leaky threads. It's a shockingly thought out design.

Last edited by Mark Parker; 11/26/21 6:33 am.

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What my friend in Poland does with those valves

[Linked Image from i.postimg.cc]

But it's quite involved mechanically with making a base for a fiber gasket, I simply locktited the threads down from the groove in the valve.

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You guys are on the right track by trying to seal the threads to prevent high pressure oil from leaking through. What this does not cure is that both the ball or piston type relief IMO allow too much oil to go to the sump. I would be interested to know if you can get 20-25 psi at hot idle and 45-60 psi at 3500 rpm going down the road with just sealing the threads. Remember, due to hysteresis, these BSA OPRV's are likely to still be relieving oil at less than 10 psi. Most relief valves are a ball type rather than a piston. I think BSA thought this might improve the engine's historically low oil pressure which resulted in many premature engine failures and warranty claims.

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Wonder if along with the O ring or fibre washer you could also reduce the diameter of the hole draining to sump so the pressure stays high even when the valve opens, the risk being the pressure can increase over the 50 psi with cold oil but unlike other engines there is no garter seal to invert so less of an issue.

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The reason BSA moved away from the ball and tapered seat relief valve was due to the possibility of the ball, not reseating due to a foreign object, something the piston type avoids.

I'm thinking that If the leaking thread on either of the std valve types can be addressed, then reducing the size of the relief sides oil bleed hole would restrict the flow in much the same way as Mike's solution does (using a smaller relief valve) to help reduce the hysteresis of the std valve?


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The piston type is more likely to stick or seize with debris than the ball valve.
The advantage of the piston one is that it does vent more.
They probably changed over as they used the same valve on triumphs.

With cold oil either valve does not vent enough pressure but it's no big problem,
as for gauges i use one when i build the engine to check then get rid of it, another
thing to cause leaks.
Oil pressure can be something people obsess about, certainly at idle, loads of old
cars and bikes would ride quite happily on 20-30psi and tick over at 2 or 3. At idle
there is virtually no load on the bearings anyway.
Failures on these motors were normally caused by dumb owners not oil pressure.

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I think hysteresis may be just a characteristic of the oil pressure control the valves are a common type. Uncontrolled bypass is limiting pump volume or requiring much more volume to try to compensate, but really it cannot. Other engines do not do this. My engines have roller conversions but they have a temperature where pressure falls in a way other engines do not.

Adam's picture is possibly a Triumph? But looks to have the bypass drilling giving more thread to seal.

I have a big gear pump on one bike and a smaller on the other. I use thick oil because it makes a difference but heat defeats that a bit. It's better but it's not how most engines behave. Pressure settles to a level with heat, but A65s tend to go lower. So it will be interesting. But it's cloudy and not that hot here so not a great test day.


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Dave Madigan built a really good oil pump for these using gerotors.
No-one was interested, maybe it's because he didn't anodise it blue
like the srm ones? As i said, dumb owners are the problem.

If you want an a65 to work well with the plain T/S bearing you will definitely
need to spend some hours rebuilding the oil pump or replace it with either
a properly rebuilt one or a new one. Then fit an oil filter and sort out the
relief valve, some are worse than others.
By the time you've done the bush properly you may as well have done an
end feed needle roller conversion anyway so that relieves 30%+ of the demand
on the oil pump.

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Well split that O ring, had one smaller and stretched it over, it went in easier but with a little resistance and went right down. You can feel the resistance of the O ring all the way down. I probably need lighter oil.

I took the spring out without undoing the main body, to crush it as much as I could, because the O ring would come off. I warmed it in the shed but pipes and head and stuff are hot but it had too much pressure. Or at least more than I want. I squashed that spring as much as I could. But it's still idling at 85psi. It stopped when revving around 110 now it's around 100 but warmer.

The cases are quite hot, but not like riding, so I have to wait on the rain to go away a bit. The only worry is the stress on the pump but 80-85 is quite normal on this till it's 30-40+ miles hot, 60-70 is ok but lots of heat like 100f + day can get it down to 40 at 3,000. It would get to a point and fall quite a bit.

[Linked Image from i.postimg.cc]


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You shouldn't need any heavier than a 20/50 oil really.
That P'rite hpr 30 is pretty good, 20/60 lots of zinc in it
and suitable for wet clutches. It's all i use in my own bikes now.
Bill always used to stick some heavyweight glue into the outfit
and blimey, did i see what it had done when stripped.It just
doesn't circulate. BUT gives great pressure ..............
Now use a 15/50 as it had a habit of inverting the crank seal with
20/60 unless well warmed up before use.

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I have 25-70 because pressure would fade away. When hot after some miles it's around 80 about 45-50 at 2000 and around 30 at idle, a fraction over 1000. I let it sit 2.5hrs, the cases were warm and idle was 90psi. But it's only 65f here today. The O ring seems to be sealing I'll see if it stays good. But this PRV I took out because it worked so bad. It now works much better.

The Ace bars are a bit racy. It's a bit of a tank though, very old school with the drums and stuff. Bars are better for how zippy it is.

[Linked Image from i.postimg.cc]


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Originally Posted by kommando
Wonder if along with the O ring or fibre washer you could also reduce the diameter of the hole draining to sump so the pressure stays high even when the valve opens, the risk being the pressure can increase over the 50 psi with cold oil but unlike other engines there is no garter seal to invert so less of an issue.


Kommando,
When I did my testing, I plugged the bypass so that the ORPV cavity was at pump pressure. After installing a tee I put a needle valve in the return side and clipped it to a glass jar so I could monitor both pressure and volume returning. When I started it cold I had to open the needle valve a couple of turns to keep the pressure down to reasonable levels at idle. As the engine warmed I gradually closed off the needle valve and once the motor was up to temp I could close off the needle valve completely and have about 70 psi a cruising rpms. That is when I realized the pump has sufficient volume to maintain pressures. Then I installed the new OPRV which worked well at controlling pressure and not allowing it to over pressure the bearings except when cold.

If you reduced the size of the return hole by plugging it and drilling a smaller hole thru the plug you would improve oil pressure as the smaller hole would simply act as a restrictor. That is exactly what my small OPRV does but it adds control with the small ball and spring that opens at 50 psi.
It's just a simple way to get decent pressure without any major modifications. I could have drilled out the bypass hole to app .310 in and pressed the ORPV into the hole. (It is made for press-in applications); however I was not sure of the thickness of the casting in that area so I elected to put in in the bypass line itself.

NickL,
I agree that motors at idle only need a small amount of oil pressure, but my experience was that if you had low oil pressure at idle, I did not have sufficient pressure under high speed and the heavy load of hard acceleration. Now the system has more than enough at adle and 40 to 55 psi at speed.

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Mine still works fine on the 64 LR - Thank you Mr Mike.

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Bill,
Thanks Bill, I haven't seen or heard from you for a long time. Hope you are doing well and still doing those hi mileage rides on these old bikes. I am just a weekend short hopper when the temp is above 65. Got the sailing bug and now have more sailboats than bikes. I am gonna make a ride somewhere this spring. Good hearing from you again.

Mr Mike

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