As Bob Wardley pointed out, one can modify the existing, in-case check valve by drilling out the original and replacing with an A65 spring.
I’ve decided to document my efforts do that modification.
I first measured the depth to the captive check ball and found it to be 16mm or 5/8”. I was concerned about drilling too far so I wanted to tape/mark the drill bit for depth control. (Later I determined that this was really not necessary)
I decided to drill the hole twice, once with a 9/32 drill, then with the 5/16’s that Bob originally recommended. Next time I would try to see if the ball and spring can be freed with the 9/32 hole, now knowing the original ball is only 8/32 (1/4).
I used lots of grease on the drill bits and cleaned each often to capture as many chips as possible. I also used a small screw driver blade wrapped with a single layer of cloth, and lightly greased to pull as many chips as I could find. I must have done this about 10-15 times (after the spring/ball had been removed) before I was satisfied I had them all.
The ball came out quickly with a magnet on a small screw driver blade, but the spring was a bear. At first I thought it was a chip blocking the spring, but as I used a small dental pick, it became obvious that all manner of junk (fibers) had collected in the spring. It acted as a small filter which was good to keep the matter from the bearing, but bad as the spring lost it’s ability to push the check ball.
Bob mentioned counter sinking the oil pump orifice to make a better seal. I had no mechanical way to accomplish this evenly. I did notice the new SRM pump was very slightly counter sunk already. The original check ball was ¼, with a 6mm ball being different by .013” in diameter or .007” per side. The ¼ ball is slightly bigger and more available at ones local bicycle shop. I used another ¼ ball along with a short piece of tubing to make a lapping tool. With some fine lapping compound, I spun it around in the pump opening. After a couple of minutes, there was a small band visible in the pump body, which assured a good fit/seal.
When I assemble it, I found the A65 spring was too short. I had ordered two kits (The A65 kit includes one ball and one spring) so I used the second spring and cut some off. Final fitting had the two springs expose about 5 mm beyond the edge of the hole. I greased the ball and stuck it on the oil pump to aid my assembly. The rest was easy….except. The gasket supplied by SRM had an extra piece that needed to be cut off, and used under the pump’s forward mounting hole. This was to ensure the pump was “level” with the case, and eliminate any possible binding.
The result has been great with no short term wet sumping. I’ll have to update this thread when I can leave the bike sit for a few weeks.
Adm edit: errors in the pictures, & please see the forum rules regarding picture posting. Fixed link to the picture series >
http://s19.photobucket.com/user/marathonpaul/media/BSA%20A10%20wet%20sumping%20project/DSCF6595.jpg.html#/user/marathonpaul/media/BSA%20A10%20wet%20sumping%20project/DSCF6617.jpg.html?&_suid=137871989593105686902947935697