I got a bmx 90cc and it has continually started running worse and worse. I've tried the carb adjusting tips from 2manytoys, cleaned the carb, adjusted over and over and after my boy rides a little while it starts running like crap. I bought a new carb and installed today and it just will not throttle up. If I hold throttle open it will backfire even though it won't run up.Please help, my 5 year old is begging too