My old eyes just couldn’t see the fins. (Still can’t, LOL) I’ll take youal’s word for it.
That 550 will make about 300 HP at 2750 RPM, won’t it? (I’m a Lycoming guy and am just guessing.) Should have enough low end torque to pull that bike effortlessly.
The motor is a Continental brand. Those engines were aimed at the sprayer part of the scheme - the CAMSHAFT drives the propeller - note the drive on the upper part of the cooling shroud. The ‘ transmission’ looks to be something out of a snow bile or something like that, I would not want to ride this thing, but it sure is eye-catching!!