Tonight I replaced my front and rear sprocket and the chain. I put a 14 on the front and a 55 on the back. After replacing the crankcase cover gasket and putting everything back together and adjusting the chain I started up the bike. Immediately I heard a rattling like something was loose in the engine and then it went away. I tested out the new sprocket by just riding down the block and back and the bike would not idle and as it was coming down to an idle as I pulled up to the house I could hear the thing bouncing around and then the bike shut off. It was also waaaaaay hotter than it has ever gotten, even after hours of straight riding. What could I have done? I made sure I didn't drop anything inside or anything. I don't know what could have gone so wrong with such an easy job?