I have run a 6V starter on 12V for 20 or so years with no trouble. It does spin the engine over faster and sounds different. It is presently starting a 9:1 CR 261 without complaint even at 0 deg. F.
What flywheel and clutch combo are you running on the 6v starter? I'm thinking about moving forward with the 9 1/8 clutch from a later model 216 that has the 7/16 bolts. I haven't figured out the clutch yet.
