Had a few beers and a question...

[Pollock]

Maybe I will think clearer tomorrow but....have you ever used a battery to check an alternator/dc dynamo to see if it motors. Doesn't mean it will work..... probably will but if it doesn't motor it won't produce current...anyhow.
I know other bikes have used a Starter/alternator. A duel function unit. Why couldn't you hook a switch with a current to the dynamo for starting flip the switch and go to charging?
Let me have a few more beers so I don't go out and try it on my super rocket. In the meantime maybe someone can tell me why it won't work before I fry my dynamo.
Peace
Pollock

[Triton Thrasher]

The dynamo on a BSA is not a powerful enough motor to start the engine and the drive probably isn't up to it either.

[Dynamo Regulators Mike]

The Bosch / Siba Dynastart unit achieved starting and dc generation in one unit. These were fitted to a few bikes, many microcars (e.g. bubble cars), some boats etc. Reliabilty seems often to have been marginal. Its design used separate windings for generation and for starting, the latter much heavier duty. A key engineering issue is that neither part is optimised for its role. To generate say 60W it would have to be of higher volume than say the Lucas E3L unit. But a neat idea.
Mike