Big Gun Exhaust 40-R07 Rev BoxBig Gun Exhaust 40 R07 Rev Box If you are looking to swap out the stock CDI box on your Kawasaki KLX 400R, the Big Gun Over Rev Box is an affordable alternative to highly priced OEM replacement boxes. It increases the overall RPM limit over the stock box and advances the timing curve. Increases overall RPM limit Advanced timing curve Easy direct plug in replacement to stock CDI box 6 Month Limited Warranty Big Gun Exhaust 40 R07 Fitment: Kawasaki KLX