The KX250F fuel injection system features dual injectors: an injector downstream of the throttle valve (where injectors are usually located on standard FI systems), and an upstream second injector close to the airbox.
Unlike the dual injection set ups found on supersport models (where the upper injector operates only part-time, providing additional fuel when necessary), the two injectors in the KX250F fuel injection system have different roles. The downstream injector is used to ensure smooth, instant response while the upstream injector is charged with providing power. As rpm and the throttle position increase, operation switches from the downstream injector to the upstream injector. (Depending on whether in a low (1st, 2nd) or high (3rd, 4th, 5th) gear, the switch is either progressive or almost instantaneous.)