Are you using a 6V or a 12V starter? There's a difference in the number of teeth on the flywheel, and the starter drive pinion, so the starter and the flywheel must match. It's OK to run 12 volts against the 6V starter, as long as you don't crank for an extended period of time, but the starter and the flywheel MUST match. The 56 flywheel will be set up for 12 volts, so you'd need to be sure to use a 12V starter, or use a 6V starter and swap to the flywheel for a 54 or earlier engine.
Jerry
