in the final phases of my project, my helical gear pin kept on sliding out of the slot and \'locking up\' the works. My solution is a very thin pin retainer tube that fits between the thrust bearing and c-bore of the rear interior plate(it\'s very thin gap). The helical gear on the main shaft keeps this tube in place. The OD is .780(minus clearance for the c-bore) and its .240 long. You just don\'t want little surprises like that, cranking away and then a \'dead stop\' clunk when the pin works its way out and jams into the crank block.