[dsraven]

I would say pull the starter and check the depth of the starter gear from the mounting flange, then compare that depth with the depth of the ring gear from the starter mounting flange. I also think there is a different ring gear for a 12 volt starter compared with a 6 volt starter. maybe the teeth are not matched up so they don't match. number of teeth on the flywheel maybe not right for the starter, or vice versa.