I have an electric start 200cc in my VBA which is hooked up to work through the old kill switch button and it works like a charm. It got me thinking about doing the same with my current Primavera project bike for something different and I've been starting to look at how it might be done. Very basically there's the same starter motor as the large frame but it has a direct drive instead of a 90 angle drive. It fits in between the shock and the exhaust outlet in the casing and extends a small gear to mate with a ring gear on the flywheel. I have the ring gear and I can easily machine the flywheel to accept the gear.
Next step is to look at the cases and I can bore a hole in the flywheel side and reinforce it with a little aluminum welding and a small collar for the starter motor (I tried to upload an image but was told this forum has exceeded it's allocated disk space). This is very similar to how the original was done.
Only issue is there seems to not be enough space between where the shock runs and the exhaust elbow for the starter. Did the electric start models have a different shock and a mounting point further back or something? Wouldn't be the end of the world to do the same thing but I'd have to think about how to reinforce the mounting point on the frame.
I have used elec start cases and not fitted the starter on standard PK's and everything seemed to be in the same position There was also the dynastart version in which the very special stator was fed a DC supply and acted as a starter motor These dynastart units are very few and far between I have only seen one in over 40 years of playing with scoots
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