What is a "rag joint" is that on the engine or with the kit? I tired to find a kit with a belt drive so far no luck. Could you provide a link to one? What is a "single chain transmission" ... like a one speed? Is the bike I'm choosing going to need those disc brakes? Are they available for that model bike? Will it be okay without the disc brakes?I assume its going to be the single chain transmission. They make no mention of the gear ratios or show a pic, probably on purpose. I would look for a kit with belt drive. Also, if you want single speed, a rear wheel that takes disc brakes would work best to mount the sprocket. The rag joint wrecks your spokes.
Like Dan says they don't show a transmission. They also don't list one in the section listing parts included. That means if they don't send one with it you will have to buy one separately. You want a kit with a belt drive. I strongly suggest that you spend a little more money and get a quality kit from a reputable company that stands behind their product and will be very reliable. This is what I would chose. you will save money time, and countless headaches in the long run.49cc 4G T Belt Drive Complete Gas Powered Engine Kit - Bicycle-Engines.com
Yes it's a belt drive trans. This is the European bottom bracket adapter you were asking about earlier. Bottom Bracket Adapters - Sick Bike Parts