No doubt that a human can put out more torque. But HP is a different beast, one hp is 746 watts and the best bicyclists make like 350 400 or so I'm reading. The energy created by a 6.5 hp motor is almost 5000 watts or 12 bicyclists.
After some reading and searching, the high end bicycle rpm's for sprinting cyclists is 170 or so. After reading that website I found out it is not all that uncommon for these racers to bend sprockets or tear a derailer off.
So to re-cap, a human puts out 400 watts max, can push a bicycle gear at 170 rpm's. Compared to 5000 watts and 3600 rpm's on a governed stock clone.
Bicycle gears are just not built to handle that kind of energy. The sprockets maybe be tough enough if you get high quality steel ones I dunno, but the gear set is held together with ungraded crap and probably rivets or some junk. The whole assembly would fall apart.
Not only that but how do you manage to de-rail and re-rail the chain on the different size gears? A bicycle pushes side to side on the chain to get it to jump on and off and uses a tensioner with a decent travel distance to compensate for the different gear ratios. I won't assume he said he was shifting at max rpm, let's say 2000, that chain and or sprocket is toast.
I'm calling shenanigans unless video is posted. There's a reason why we all don't have a setup like this on karts.
