I have a 300ex with a Uni filter and a big gun "quiet" exhaust. I was wanting to get just a little more out of it. I was thinking about getting a 400ex carb, are they worth it. I have been seeing alot about using a sparks high-rev cdi. If you know of any other mods that can be done without breaking into the motor I would like to know about them. Any help that you are able to give me would help me alot, thanks alot for your time, help, and patience with all my questions.

 

if you have a filter and pipe youll need to rejet the carb if you already havent to keep you from running lean. the 400 carb isnt worth it with the basic mods. rejeting your will be fine. the cdi box is a good piece for the 300 biengs it revs out way to fast once you install a filter n pipe. other goods mods would be to change your sprockets or even a hot cam which is pretty simple to install.

 

the 400 carb isn't worth the trouble...best to just rejet your stock carb.

Depending on your type of riding, smaller rear tires will offer quicker acceleration and better handling than taller ones...which is good for racing on a track. As GSJEEP states, a sprocket change and a better cdi box, plus a cam are the way to go. A few years back, Dirtwheels had Four Stroke Tech build up a 300EX that would run and hide from a stock 400EX...always thought it would be cool to see them run it against a stock 450