I saw those when I was looking for a source for the awesome ring and pinion trannies. I wonder how they achieve such a high displacement with that style motor. I have the 52cc one and that overboar is the largest I've ever seen sold for power equipment and pocket bikes, usually the next step would be the reed and high comp top end kit with billet head (which isn't worth buying, because you can get a stage III Cagllari with all that for around $100). I bought it for use on a daily rider bike since the transmission is mega beefy and 33:1 (regular bicycle wheel sprocket gearing!) and the motor doesn't have reeds to inhale when they eventually fatigue. It also comes with the option of a replacement plan at HF, so if it pops this year I'll get a new one and rip on.
I love mine, its a great affordable chain drive if you put a 7/8" freewheel adapter keyed onto the trans. I think it would perform a bit better with a gravity fed carb versus the pumper because sometimes you get a pressure pulse feedback that causes oscillation in the revs, which you can overcome by playing with the throttle a bit or just gassing it and ripping out of the hole. Putting a less restrictive filter on and an expansion chamber, and lightening the clutch shoes with a drill seems to have tripled the power out of my "1.5 HP" auger motor, which is really only rated that low because the clutch stall is like 4000 rpm stock and the EPA tuning and baffle box muffler are meant for noise and emissions compliance, so it never gets into the powerband, which on my BMX in its current setup is from 8500-10600.
