So I bought the The 49cc Hausheng 4 stroke engine kit. I was originally going to put it on my mountain bike, but do to some clearance issues I had to mount it to this. Now the rear wheel on this bike can either be a fixie (Rear sprocket is a brake) or just a regular free spinning sprocket. I currently have the chain in the free spinning position, leaving the Fixie side free. Instead of mounting the rag joint can I just put the chain on the 18T gear on the back? I'm unsure if 18T is too small to get any appreciable torque. I also just want to be careful about putting to much stress on the rear wheel. There is still a lot left to do on the bike. The biggest issue is changing the ram's horn handelbars. Again it wasn't my first choice but it works. I just want to make sure that I do things safely and correctly. **EDIT** Figured it out. The engine wouldn't be able to do the low gear justice.