ebmvegan, I'll be using two separate throttle controls. No need to synchronize engines rpm. "Mr. Hyde" runs well with a 1.25" friction roller up front and a 1.50 friction roller in the rear. No problems whatsoever with these independent engines. The front engine supplies the low end and midrange, and the rear engine supplies a little low end, some midrange and all of the top end. At 25mph, the front engine reverts to idle while the rear engine screams to redline.
I'll be installing a 10-tooth jackshaft/44-tooth(4.4:1) front sprocket up front, and the rear wheel has a 36-tooth(3.6:1) rear sprocket. So the front will peak at maybe 30 mph and the rear engine takes over to redline at 38mph.
Later on, I might use a 12-tooth jackshaft/44-tooth sprocket, which would factor down to the same as a 10-tooth/37-tooth drive(3.67:1)
Then both engines will supply identical power throughout all ranges, even at redline.
I have seen Cushman scooters from back in the dayz, being the late 60's when those wide beast were used mostly in industrial plants and ship yards.
They had the engine mounted directly over the front wheels and had a cargo bed to haul heavy loads and parts delivery for the yards. Very reliable in moving loads, front wheel drive proved its worth with Cadilac back in the late 50's. Worth the time to set up and enjoy.
Well, I trial fitted the sprocket onto my stock front wheel. It won't fit because the hub's axle register is way too small. Maybe the rear coaster hub and wheel would fit the fork, or a front disc brake hub with sprocket adaptor. Another option would be a custom sprocket with smaller axle register(hole).
Nah, I'll just keep the front friction drive, spend a few bucks and fabricate the engine lift. My main concern is to eliminate resistance drag from the friction roller, especially when front engine is idling and rear engine is screaming.