Here we go on another starter project - not that the bike is hard to start, just that it's not recommended kick-starting bikes after a hip replacement. This time it's my 800cc 50* vee twin fitted in a '49 M21 frame. I've usually referred to is as GB50V but have morphed it to M21V2 on this forum.
Anyway, made a start a week or so ago sketching what might work and decided to drive the crank via a cogged belt, being as there's no room in the (tin) primary case for starter gears etc.
Yesterday and today been creating the first part, the pulley to fit the crank. Bit of a struggle, as the spacer between engine sprocket and pulley has to be fairly thin - the OD small enough not to foul the primary chain, but the ID big enough for the cush drive spring to fit inside. The spacer is bolted to the sprocket with M5 allen bolts, but welded to the pulley. The latter is where the hassle lies - needing a good arc penetration without destroying too much of the teeth (adding to the compromises was limitation of pulley OD to compliment the outer primary case). Obviously had to remove the belt guide for welding, then opened it out to fit over the spacer and silver-soldered it back in place.
Unfortunately a similar situation as the spacer / pulley hassle will occur with the gear on the sprag clutch. The gear is not wide enough and will need a collar added, again welding right next to gear teeth. Of course, a more elegant solution would be to machine the required teeth onto steel bar, but I don't have stock of appropriate material in large enough diameter, and shudder to think how much a special order of 4" dia EN36 or similar would cost (probably a minimum order of 1 meter). Furthermore, I don't have the cutters required. Yes, MOD 1.5 involute cutters are available at very reasonable price, but not sure about a cutter for the pulley. Might end up having to fly-cut it, and the usual problem with that is that the cutter gets tired before you reach the end. More grief I don't need, hence doing the way I chose.
