There's some pretty complex geometry involved in making the foot start system work properly. A tiny bit of wear or slack at several pivot points, plus a little wear on the flywheel ring gear can combine to cause the problem at hand here. There's no quick fix, and no way to adjust anything. Tackle the whole problem one step at a time instead of looking for the "easy" button! The engineers did a lot to solve the grinding problem by making the 12 volt starter drive rotate slightly as the starter gear engages the flywheel, but there's no way to make that happen on a 6V setup. If the pinion jams against a flywheel tooth instead of engaging smoothly, and there's enough slack in the linkage to let the motor start spinning- - - - -GRIND!
Jerry
