The best way I know how to tell is the flywheel. 4 teeth per inch = 6v, 5 teeth per inch = 12v.
Yes, counting the teeth on the flywheel will confirm 6v vs 12v. [flywheel]
But, it is not so easy checking for a 6v vs a 12v starter. The number of teeth are the same on 6v and 12v starters. Last summer, I caught a rebuilder (who knew better) using a 12v drive gear on a 6v starter rebuild. He said the number of teeth were correct for 6v. I showed him the parts book.
If I am correct, will counting teeth on the flywheel confirm the voltage of the starter that is being used with that flywheel (counting the teeth on the flywheel confirms that the flywheel was made for 6v or 12v)?
Am I incorrect about there being the same number of teeth on the 6v and 12 starters? If I am correct, counting the teeth on the flywheel will not confirm which voltage starter was being used with that flywheel?
