i was just wondering what are a few things i could do to make my 400ex faster that dont really cost that much money

 

Partially, it depends on the type of riding you do.

Run a 14 front sprocket. It will make it accelerate quicker but you will lose top end speed. This is a great change for trail riding and on the mx track.

Get a Dynojet kit ($50) and rejet without running the lid. It is worth an extra 1-2 hp. It is not a huge change but you can differently feel the difference over stock. If you aren't concerned about noise level, then a full exhaust will provide additional hp.

If you are riding on the track, run 18" 2-ply rear tires.

Changing your handlebars will make you more comfortable riding faster. Basically, you will be hard pressed to harness the existing power in the trails if you don't upgrade the stock handling. There aren't many people that can run a stock 400ex for all it is worth in the trails or even on a track. Now if you are strickly talking about riding fast on a drag strip or a long straight away, then anyone can peg the throttle and hang on for all it is worth.

/jon

 

I agree. Removing the airbox lid and rejetting the carb is a great place to start.