http://devestechnet.com/Home/Flywheel

That explains the issue you are having. The starter's gears are not easily interchangeable between 6 and 12 volts. If you have a 6 volt starter, you have 139 tooth flywheel, if you have a 12 volt starter, 168 teeth on the flywheel. Flywheel ring gears are reversible as explained in the document above. Starter parts are not interchangeable unless you are a machinist. (not sure about just turning the gear around.) It's amazing you are getting it to engage at all. Then you are destroying your flywheel over time.


Deve

1950 Chevy 3100 Deluxe Cab
1950 Chevy 3100 Standard Cab
In the Stovebolt Gallery
The Think Tank
More info and tips at Deve's Technet