Twin Bike Sports Runabout
 

Engines synchronized by common distributor

Bikes already suck vs cars re payload moved/gallon. This twice as bad.

This is just for fun!

Until you turn. :rolleyes:

Yes, some method of de-clutching the inside wheel activated by the steering, perhaps electrical clutches on the rear wheels.;)

Yes, but 90 deg out of phase with each other so that there are four single power pulses each revolution, rather than two double power pulses. This can be achieved through the use of an eight cylinder distributor shared by both engines.

The closest to that I've seen were projects for wheelchair-accessible trikes, but those resorted to scooters instead of traditional motorcycles. But I'm not sure what had been done to keep the engines synchronized.

Maybe, the easiest system would be to place the two engines behind the rider, and join them physically, 90 degrees apart, with a double sprocket idler shaft, and drive a single rear wheel, making it a twin engine trike. Slightly lighter, easier to turn, and easier to license. The reason for connecting the engines 90 degrees out of phase is to have 4 instead of 2 power pulses per revolution. Smoother, and sounds better.
(Something like this:)

Let 'em be "unsynchronized"- twin engine aircraft make no attempt to phase crankshafts; matching rpm is sufficient.

Twin engine aircraft don't drive a single wheel, and drive, instead, a fluid. In addition, to provide for rpm differential to aid in turns, the two aircraft engines have to be able to operate separately. Again, twin engines provide limp home capability. On the other hand, I believe some twin engine aircraft DO mechanically join the two props, so that one engine can turn both, if the other goes out.
I don't want the engines to phase in and out with each other. Those vibrations would be far less pleasing than eight evenly spaced firings.