kawasaki prairie 360
Welcome to the forums and speaking from many many hours of research and experimenting myself like Jamakn says enjoy what you have and don't pour any money trying to make this bike go faster!
The only thing I did worth while that made a diffrence for me personally was to raise my needle valve in the carburator .060 That modification really stepped up my low and mid range responcivness but did not effect the overall top end speed of the 4 wheeler. I have a picture of it in my profile page. It is an easy mod that you can do yourself. Now that being said, I also experimented on my prairie 300 and no matter what I did to the needle valve the bike ran worse!
I tried 3 diffrent exhaust systems and all three sounded awsome but all three caused a lack in horsepower. This was tested on an 1/8 mile drag strip with timers. This is a very low compression motor and requires a lot of back pressure to operate properly. The stock exhaust makes the bike run the best.
Good luck and if you come up with something than great for you and please do share with everyone else. I am not the only one to make several modifications to this machine without benificial results.
Again welcome to the forums,