12v is 12v. Your alternator doesnt care if your battery is 2Ah or 200. As long as it fits, it doesnt matter on whit. Quality of batteries may be an issue down the road, but 12v is 12 and as long as you can fit the battery on the bike in some way, and get some wires bolted to it however, its go.
It aint a fit night out for man nor beast.