Want the ultimate, rather cheap diskmotor, Go ICE.
Internal Combustion Engine.

There are 2 for sale around here.
1 22 hp Suzuki RM125 cc, already lightened and RWd.
1 32 hp Suzuki RM250 cc, also with empied gearbox and stuff, This one was plan C for Tough As Nails, but we never came to it,as the cost for the hydraudrics was to high for our meager means.
Both motors are in parts, so the future owner can learn what he has.
The 125 cc is going for £80
The 250, any offer will be looked into.