Man, I bet you two chains I could find a. 116h that can withstand the punishment of a lifan 125. At least, that's the standard 6-8 speed length. 116l is what is commonly used for bicycle chains. Perhaps if it was a 116h half link chain? I'll take a look. Also, internal gear hubs can take up to 420 chain with a bit of professional modification.Actually, with the current gearing, 1st and 2nd gears are pretty much useless, topping out at about 5 mph and 12 mph. That's why I said I could go much faster if I wanted. I'd just switch out my 40t for a 20t and I'd double my top speed. Also, there's no way a standard bicycle chain would withstand the torque that the engine puts out, so shifting through the rear hub is out.
UPDATE : it turns out that the alpine 7 speed and the nexus 7 both have removable sprockets, but you'd have to use that original as a base for your slightly larger, wider one.