just bought a used 2000 300ex for a first bike for a 14 yo it runs for a short time then bogs and missfires the air box and carb were very dirty and i am going to competely clean the carb filter and fuel sytem and new gas and startron fuel additive also check the compression it runs great at idle when first started then when warm it seems to be rich black smoke it does not need to be chocked to start either and other suggestions would be helpfull hoping some of you have had some experience with this model

 

It was bad gas and dirty carb cleaned and added textron to the new gas