C2 is biult like the V1 with an internal variator. the C3 has a motorcycle cylinder from a minarelli P4 or P6. on a bad day with a 19mm they were 6.5hp stock and restricted.
the C2 runs a the cylinder from a V1 the V2 also does. the C3 runs a cylinder from a dirtbike basically. you can get over 30hp from the water cooled version. they also came as 4 speeds with pedals called the P4 but the head was not the same