I think I'll order a spare soon also. Thanks for the link. This got a bit long for a discussion on sprag sources but I got carried away.
A sprag story -- I once had kick-back flip a sprag over-center from a low battery and a Boyer MKIII. The result was ugly. It flipped over just as the motor caught, which spun the starter to a million RPM. I managed to get the armature out of the case with a 20-ton press. Amazingly the sprag parts survived. I built up a new starter and installed a new sprag.
I carefully checked the torque on the limiter at 50 ft. lb. At that setting it wouldn't hold the torque of a modified 4-brush Prestolite (Harley field and brush rack) driven by a 20AH Goldwing battery and big cables. So, I set the limiter up to 55 or so, which mostly cured that problem. With a newer-design Boyer I have not had kick-back problems but the torque limiter lets go sometimes with an awful noise. I don't remember whether I have a 14 or 18 tooth sprag but it hasn't given any trouble. I believe I got it from Old Brits about 20 years ago. One issue with the torque limiter is that if it lets go repeatedly, the little holes the balls live in get a bit of a track from the balls escaping. That weakens the torque limit of the unit.
I dealt with many of these back in my wrenching days and found that keeping the primary oil clean extends the life of the sprag dog-bones. If there's clutch swarf floating in the oil it acts as an abrasive and wears everything, chain, sprag, chain tensioner and all. Also ATF seems to provide better bite for the sprag and a nicer clutch feel than motor oil, despite the book's recommendation.
Another sprag story -- A couple of years ago I bought two sprags for an e-start Royal Enfield Bullet sidecar outfit (500cc) off Amazon. A Bullet should have a little less strain on the sprag than a Commando, having lower compression. Enfield has no torque limiter. Bad! Enfield has owner who mucks about unnecessarily. Bad!
At the time I installed the first one the running surfaces were good. As part of that job, I also replaced an electronic ignition whose make I don't remember with a Power Arc unit the customer supplied. I purposely set the timing a tad retarded in an attempt to save the sprag. While out of my hands, the owner mucked about with it to the point it wouldn't start at all. It came back on a trailer. I reset the little timing gizmo which had gotten way off center. It started right up but the sprag was very unhappy and complained. On the test ride I took it by the owner's construction job site and when I went to restart it the sprag cratered. I couldn't kick start it either. The engine was locked up. Back to the shop on his trailer. Dismantle the primary. Sprag is all in pieces. Running surfaces are ruined.
I eliminated the e-start parts and gave the owner the somewhat complex Power Arc starting procedure from the Old Brits website. Following their drill it starts right up but the owner can't seem to understand the sequence and it kicks back on his foot. He's not happy. So with a progress payment from his project he bought a Ural sidecar outfit. So far so good. It starts and he's bought a bunch of accessories for his upcoming trip across Asia. He'll be 80 when he leaves. But the Bullet still sits there whimpering. It is a much better-looking classic bike and he'd be right at home in India. But I digress. Now I'm looking for an ignition system for the Bullet whose starting drill is dumb-simple and that won't kick back no mater what. And if I find one, I may suggest that he spring for new starter parts too. I say that advisedley as it's had many sprag problems and had a bad sprag when he bought it.
