I have a 1996 trx300ex and i have a problem with the jetting..
where is the jetting located and how do i check if its the right size?

 

What kind of aftermarket parts do you have on it? If it is stock or you only have a pipe and some kind of aftermarket air filter I would recomend a stage 1 jet kit from Dyno Jet. If you have any more parts on it than that I would go with a stage 2. Dyno Jet jet kits come with detailed instructions that tell you where the jets are and pretty much everthing you need to know. They also have a trouble shooting guide as well. I think they sell for about $55-$60.