Hi I am a newbie and I started building the bike over the summer and gave up! But, a month ago, I started again and finished and got it working. After about one tank, and a few little kinks, the chain started to fall off every time I would ride it! I replaced the chain with a heavy duty #41 chain, but when I'm riding, I hear a knocking sound and then the chain pops off and I skid and can't ride. Thanks in advance for the helpful advice!!!