I've thought about just using a 20" rear wheel with a track hub and 20 tooth or 18 tooth track cog on the left side. That ought to give plenty of range with the stock engine's RPM band.
I think BIOpace rings would be good for serious diesel leg mashers and maybe loaded touring bicycles. I tried it on a road bike and it was fun for a while till I learned to pedal circles. :-) I think I wore out a derailleur spring before I gave them to a collector.
All these ideas are fun, but I'd just buy a 2speed stock moped or a Shift Kit for happytimes and get it over with.
Originally Posted by Goat Herder
They do very slightly prolly helps shifting better.
Remember the old Bio pace sprockets? They faded out rather quickly. Turned out the folks using the normal sprockets were winning all the races.