Making a 2 smoke run backwards.

[fabr]

you are correct about the bendix. I didn't say the bendix would work by rewireing the field windings.To do that you are correct that the old starter/generators worked because they could be constant mesh.
 Newer electronics that have the reverse rotation would be programmed for the reverse rotation and the normal rotation.With older electronics a second (switchable) pickup would do the trick.

[Nutz4sand]

The golf Karts I have seen with the electric autostart use the generator/motor combo connected by a belt (no bendix) The driver steps on the gas pedal and the electric motor starts to spin in the desired direction once the motor can fire it does and then it in spins the generator to recharge the juice taken out of the batteries. Works great but limited rpms somewhat. Perfect for a putzy golfkart.

My Grandpa had a Simplicity lawn tractor that worked the same way. It was a four stroke so it would not run backwards but the generator/starter were one and the same and connect by a belt and pullies.  Genrators (of old) did not like too many rpms or they would sometimes throw the windings. Dunno if a newer setup could be used like this that could deal with serious rpms.

Maybe a belt setup that got loose once running like a lawn mower disenguages a drive belt in a deep "V" pulley? 
 

[Camel]

I am not that familiar with twin sled motors, but I had a 1973 Yamaha 250mx that would run in reverse.

Tim,

same here, a white Yamaha MX400 that was a pig to get running right.  I was mucking around with the (cutting edge back then) CDi timing at a MX event.  Got the bitch to the line, kicked and kicked and started it and when the green flagged dropped - I shot backwards.....

Camel