The two piece rim/centrifigul clutch is an interesting solution to effect an idle.
I'm sure that with some thought there could be a way to do it. I'm just wondering if the way to throttle the engine would be thru the carb or the sequencial ignition to fire the cylinders as a hit and miss. Running on one cylinder and then bringing in the other two once under way.
When I was at the Wright-Patterson AFB museum I noticed several early aviation engines had valves with open external springs which weren't activated by any mechanical linkage. Just the vacuum or external pressure caused it to open and close. It was the first time I had ever seen such an arrangement. I'm sure the valve in piston worked that way.
As a matter of fact that powered pogo stick of mine (the PopRod/PoGoGo) uses a poppet valve in the piston.
I'm figuring a 3 cylinder radial with 20 to 25cc cylinders (like a small string trimmer motor) would sit within a 12" diameter circle on a 3.5" wide crankcase. So there could be room to construct the rim within a rim.
I'm thinking of that mono wheel motorcycle set up on a smaller scale.
With the two piece rim & centrifigul clutch configuration, it may take some thought to find a solution for manually locking the two parts of the rim so the bike could be pedaled...as otherwise only the center portion of the rim containing the motor would be connected to the sprocket chain.
Any thoughts on that ?
Photo of the mono wheel motorcycle below.