K I just rebuilt my little 2000 RM80 and it was a B*%#$ to start. I broke in the piston by taking 2 easy 20 min rides and a little 3 ride to make sure. I let the bike cool between rides but after the 4th time i tried to go more than half throtel but it would just start bogging. Then i took it for a longer ride, well my freind did and after about a half hour we shut it off. It didnt start back up again and we even tried bumb startin it. When we came close to starting it would just backfire. Idk I might need a new spark plug so i'll try one but the plug sparks. Have any other suggestions why this might be happining?