A10 anti wet sumping ball valve modification to A65 setup photos and dimensions

[mikeb]

I know its an old thread, tho can I clarify some points about this mod.

Is this exactly as the a65 anti wet-sumping ball valve design? I ask as the original a10 design has the ball pushed out of the oil passage and the oil flow only minimally impeded as it travels through the 7/32” oil gallery hole from the pump to the timing side bush. I guess the ball isn’t fully pushed out the way but mostly.

But this design has the 1/4” ball still inside the enlarged 5/16” oil gallery passage with the oil passing around the ball.  The area around the ball for oil to flow past is about 25% less in the modded version than in the original.

So:
1. Are we concerned about reducing the oil flow with this? Or am I overthinking things again?
2. And did anyone figure out the dimensions of the ideal spring with the mod when still using a timing side bush? Like RD, I’m fairly sure the a10 spring 67-1400 is shorter and lighter than the a65 spring 68-0353 even tho some suppliers list the same for both
3. and RD – did you ever progress your idea of a sleeve in the enlarged oil gallery which the original ball seats against?

thanks

[RDfella]

Mikeb - in answer to your point no3, I was replying to Kiwipom's article - wasn't my idea.
I did change to the A65 system though. Drilling out the hole behind the pump (with an airline in the relief valve socket to keep swarf out of the oil galleries) allowed spring and ball to shoot out. Then plugged the end of the hole 'till just behind the gallery to main bearing. I machined a nipple in the centre to centralise the spring, so it wouldn't simply be lying in the bottom of the bigger hole. But it made little difference, mainly because - I believe - the A10 spring is too light. The bike now wears a valve below the oil tank, as I got tired of the hassle involved with draining the sump before every ride.

[chaterlea25]

Hi All,
Mike, I have run my SR with the modification for almost 20 years and a fair few miles, and it is still going great
(doing better than myself!!)
I have a SRM pump fitted and the wet sumping is not an issue worth mentioning
With the original pump it did wet sump as although reconditioned oil leaks out either along the drive spindle or through the mazac which can be porus, which is more than likely what is happening to RD's bike

John

[mikeb]

RD - was yours a roller conversion or a bush? i ask as the spring (25mm long) sits in a 20mm deep gallery with the roller conversion. But its a 25mm deep gallery with the bushed engine. So with this mod, would the standard spring be too short to stop wet sumping with the bush? maybe a longer spring would help?

has anyone had success with this on a bushed engine? Chaterlea - did that huntmaster wet-sump with the 25mm spring?

I don't have a set of a65 cases lying around to measure how far back the gallery sits - that would be interesting.

cheers

EDIT: pic below added re engine with bush - all measures a bit more or less, mix of old and new money.

[RDfella]

Mikeb - that sketch is just what I asked for ages ago. BTW, my A10 runs with a timing side bush. I'm of the 'it's perfectly adequate unless maybe you're racing' brigade.

[chaterlea25]

Hi Mike,
The Huntmaster engine is still on the bench, Waiting for a few small parts
It still has the original oil pump so I am not expecting 100% success on the wet sumping issue
I will start a fresh post on its PRV issue

John

[mikeb]

RD - with the bush, would it be possible that your wet sumping (post mod) was coz the a65 spring is 25mm length and the depth of the gallery is also 25-ish mm? ie no tension on the ball?
I also have the bush and am getting cold feet about this.

[chaterlea25]

Hi Mike,
The spring is compressed by the ball bearing, so the best part of 1/4inch..

John

[mikeb]

John - my point is with the bush, the gallery is 25mm deep so there's no compression. with the roller bearing and the shallower gallery there there would be compression... yes? at least this would be so if my measurements are correct (bush setup - the 'modified' section of the sketch above).

[chaterlea25]

Hi Mike
  The depth is more or less the same length as the spring, but the ball is pushed into the hole
by almost its full diameter by the pump

John

[Rocket Racer]

https://cybermotorcycle.com/archives/bsa-a10/mybsaa10rollerconversion.htm
Mike,
in one of the roller conversions that's published, the spring pressure is set by a spacer behind the a65 spring.
Was just attempting to reassemble my race engine and have managed to misplace that spacer and spring 

[mikeb]

That conversion page is interesting Tim. I've got a spare new SRM a65 spring if you need it. No spacer, but I do have a spare longer grub screw  if you still use one (3/8, 16 tpi from memory)

[Rocket Racer]

That conversion page is interesting Tim. I've got a spare new SRM a65 spring if you need it. No spacer, but I do have a spare longer grub screw  if you still use one (3/8, 16 tpi from memory)

Thanks Mike, would like to take you up on that. neither of the two main local parts suppliers have them in stock and would like to get pump back on. Ordering from offshore for a spring or two seems overkill. The a7 race motor will get this mod ( the a65 ball valve) when we do the crank this year .
I did find my engine case grub screws ok and there should have been other bits with them  . I might need to come visit ...

[CheeserBeezer]

A friend of mine suffered a couple of partial seizures (the bike, not him, fortunately). I asked him to check the oil flow back into the tank and he said it was OK. I went round to his place and thought that the oil flow back to the tank looked weak when compared to the return on my bikes. The engine had the SRM mod which included the A65 ball valve conversion. We swapped the oil pump, still no improvement. So I removed the A65 type ball and spring - problem solved, a dramatic improvement in return flow to the tank. I can only assume that the spring behind the ball was becoming coil-bound and blocking the hole to the timing side bearing, or some other similar failure. The drilling, size of ball, and length / gauge of spring are critical. He now runs the bike without the anti wet sump valve and, remarkably, doesn't seem to have a wet sumping problem. Presumably the oil pump must be in very good nick! The moral of the story is, if you're going to do the A65 type conversion, proceed with caution!

[JulianS]

To add to the comments about the A10/A65 spring -  this is the one I removed from an OIF A65 during summer 2021. The bike was a derelict and had been laid up since the mid 1980s ( no doubt due to 2 x frame fractures)

Length of spring is 20mm not including the ball.