Feedback Score: 0 reviews
Join Date: Jan 2011
Location: Smack in the middle of Illinois
Thanked 287 Times in 282 Posts
You will gain a little mid range and top end, but lose a little low end. If you got a pal you want to beat in a drag race or just out run in a flat all out high speed run, it might be worth it, but for all around fun, the stock set-up is best. In my opinion anyway.
I just spent $2500 on a 2005 400EX to get it right. Took off an HMF slip on and put on a stock muffler. Jetted the carb back to stock, removed the performance air box and installed a stock air box. Plus fixed all the brakes (including a new rear brake caliper and caliper mount), installed a new axle carrier, new front wheel bearings and fixed the reverse lockout. Now it's a blast to ride. Before it was hard to start, didn't want to idle, had terrible throttle lag, was obnoxiously loud (hurt my ears even with a helmet on) and would not out accelerate a TRX250X.