I have the 70cc kit on my maxi, I'd say quality wise the kit is somewhere in the midrange. I had a screw strip out on the reed block just unscrewing it to replace the reeds, and had to chase the threads where the intake and reed block bolt onto the cylinder.
Power wise, I am up to 45 mph so far. My pipe is holding back the top end, and I'm quite heavy for a moped, plus its still running rich. I think there is some more in it with more tuning.
leo vince hm pipe
ported case to match
boyensen carbon reeds
50cc HC head
I am going to be nailing down the jetting more, swapping out the pipe, trimming the intake on the piston. I think that will get me up to the 50mph range but it doesn't seem like a 55+ kit to me.