oh and i was thinking of this for a bit, using a modified centrifugal clutch (modified so that the weights were light enough so at the lowest setting it did not engage) or a belt system with some sort of manual clutch to engage the belt with friction may actually be viable if there truly is not enough torque from the engine to the tire to bent or break the crank shaft or key. that being said, i would look to make sure that it did actually have a key, otherwise you would just notice backfiring, then not starting, and then need a new crank. which would bend again.Hassle definitely. But it would still be interesting, I'm seeing these large 100 cc duel cylinder airplane motors around:
http://m.ebay.com/itm/281926793720
Wonder what that would be like, I know it's nothing compared to a 5 cylinder radial aircraft motor in a bike but still would be cool.
Thinking of sticking it in a chopper style bicycle.
also, i would look to see if the total displacement of the engine is what counts or if its per cylinder, if its per cylinder, whats stopping anyone from using two grubee engines geared high, front and back to get more power.. i found a brake lever that pulls two cables, adding a manic mechanic adapter to the front wheel and mounting it above the front fork is totally viable if you can weld. two dual brake levers, one for both clutches, the other for both brakes, and the throttle built into these brake levers (thumb throttle) one per motor, independent drive systems. probably cheaper too, not counting custom fabrication of a front fork with a motor mount. plus two separate carburetors, so dual fuel is totally viable, and two wheel drive. you could even use that pin release sprocket mount on the front and rear tires so you can completely disengage one and say the other is a backup with the po po none the wiser. with the aviation engine, if they wanna bust your balls you cant just pull off a cylinder and go "look its only 50cc". i mean, in terms of asthetic appeal, yea i guess its kinda cool, i cant argue that, but if i had to choose my scooter over a mint looking Harley that ran like crap, id choose my scooter every time. (actual yamaha zuma 125 scooter, not my gas bicycle scooter)