Hi Bart.
Dont know if you got this sorted but gen1 and gen2 are quite different, i got a spare gen1 motor and the guy who i got it off got a gen2 in replacement, the gen2 motor wouldnt run in the gen1 bike altho he did get it running eventually, i'l try and get you info!! The chain must be different in that the gen2 is 24 pins between in/out cam sprocket gen1 is 20 pins as the nornal B4.Keep the posts going as i run 59mm pistons already and now have a 71B crank, but as we both know these tings are SLOWWW to complete.