well i recently did my first valve job on my 04 yz450f and man was it a pain. the buckets didn't want to come off and we put it back together and took it apart about 20 times! finally got it all in spec and timed up but now i have it all back together and the damn thing won't even kick over. i finally got it to kick and it just let out one huge backfire. i weigh about 180 lbs and standing full weight on the kick start lever wont really kick it over. what did i do wrong? also have one piece left out. its a black plastic piece. probably something for the change. kind of in the shape of a crescent about 5-7 inches long? sorry i'm a newb to this and don't have much time to look it up. any help would be appreciated.