One push of a button fires up the KLX400R's engine, via a lightweight starter motor. The responsive power stems from a double overhead cam, four-valve, liquid-cooled dry sump engine that boasts rapid throttle response at all rpm. A nickel-silicone-phosphorous-plated cylinder provides excellent heat transfer properties and is host to a forged aluminum piston, which receives oil cooling through a crankcase oil jet. A twist of the throttle demonstrates that torque is on-tap from the low-end to the mid-range, and continues all the way up the powerband. Crisp and quick throttle response is provided by a Keihin FCR39 carburetor, which drinks from a long-range 2.6-gallon fuel tank.

For easy maintenance, a cable-operated clutch with a separate outer cover operates with the compact five-speed transmission. Equipped with a gear for any off-road situation, the KLX400R's transmission can handle anything from tight, sandy or rocky terrain to high-speed hard pack.

Wrapped around the responsive engine is an equally responsive chassis. The KLX400R is slim, nimble and easy to throw around the trail. Bolted to the chrome-moly steel frame is an aluminum subframe that provides a skeleton for a smooth transition between seat, tank and bodywork. Giving the KLX400R a plush ride is a 49mm long-travel cartridge fork, which features rebound damping and adjustable spring preload. A lightweight aluminum swingarm and rear shock with high/low-speed and compression damping adjustability compliment the fork and overall chassis package. Prime stopping power comes from front and rear hydraulic disc brakes.