What Tim is asking is the flywheel 139 tooth or 168? The 139 is the standard 6V arrangement and the 168 is 12V. Both have a corresponding starter drive gear. A 6V starter will live forever even when run on 12V. What won't work as well is a 6V solenoid on 12V. The advice I was given was that although it will last, it will hit the flywheel too hard and be too hard on the flywheel teeth.
