I just purchased a 2002 Sportrax 400ex. I plan on racing at my local track and maybe a few others. I currently have a budget of $500-$700 to gain some much needed low-end. I'm open to any and all suggestions even if you haven't actually done the same to your quad. I appreciate the help, thanks.

 

Put a 14T front sprocket on it. 15-20 bucks, and great bottom end. I even put a 13T on mine when I went to 22" Holeshots.

 

Don't worry about the power. Work on handling. Check into some a-arms and shocks. You can get JD arms for 445 and works shocks for 300. Put a set of durablue spacers in the rear for about 60 and take a ride on a totally different bike.
Horsepower is nice, but if your bike is too narrow to corner or jump at high speeds, what good is it?

The smaller sprocket up front is only going to rob your low end power. It will give you a higher top speed, but how many times are you going to have your bike wide open in a race. Races are won from corner to corner not on the straights.

 

Well for around $300.00 you can do a cam and piston.If you do the work yourself.Also buy a filter and slip on.It will give you alot more power.I agree with Fourwhls though,after doing my motor work I really had to get into the chassis.It was alot more power than what the chassis was made to handle.I don't know if I would buy the $300.00 Works shocks,I would save a little more and atleast get them with rezzies.None of this is cheap and sure adds up fast.I've done a little here and a little there...what can I say, I'm on a budget.

Jim

 

Fourwhls, a smaller front sprocket or larger rear gives you more bottom end. A larger front or smaller rear gives you more top end.