i just purchaced a used wr400 and need some guidance. the bike had the airbox baffle in it and the ex.baffle,I removed them,what should I rejet the carb with.I live in pa around 600ft above sea level. Ionly rode the bike once and it was backfiring and sputtering. but it only did it some time. the previous owner removed the thorottle stop completley. the bike is very hard to start if it starts at all. but i've only had it 2 days and am new to the 4 stroke thing. any help is greatly appreciated.