hi mark,
i,d stay away from the kl600 hybrid, the rg400 motor is a weak motor, i,d go for the 750 any day of the week, just check the condition of the sprocket output shaft, they,re a weakness if abused ( all 750,s are abused ). if not using it as a bike then i,d suggest replacing that shaft but think its a motor apart jobbie
the nicest 2 stroke i,ve ridden is an ex korki bollington kwak h1r,1970,s coffin tank & oh so sweet sound when giving it some,the exit pipe size was about size of 1penny coin,i felt honoured to ride it.
ordered my steel today
cheers
andy