How to Make a KFX 400 Faster

Founded in 1896 by Shozo Kawasaki, the Kawasaki company was originally a ship manufacturer, but is now widely known for its motorcycles and ATVs. The KFX 400 is a part of Kawasaki's sport quad series, which place a primary focus on speed and agility as opposed to their "BruteForce" utility quad line. Increasing the speed on the KFX 400 can be done by improving engine performance, reducing the quad's weight and altering the gear ratio.

Things You'll Need

  • Socket set
  • Torque wrench
  • Chain break tool
  • Hammer
  • Screw driver
  • Reduced tooth count rear sprocket
  • Light weight handlebar assembly
  • Performance carburetor/engine kit
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Instructions

  1. Altering The Gear Ratio

    • 1

      Remove the left rear wheel from the axel in preparation for swapping the rear drive sprocket.

    • 2

      Use a chain break tool to disassemble the master link of the drive chain. The master link will be denoted with an M, or can be visibly identified by its removable rivets.

    • 3

      Unbolt the sprocket from the sprocket hub and slide the sprocket off the axel. For increased top speed, choose an aftermarket sprocket with 2-4 fewer teeth. This will sacrifice some low-end torque, but increase your top-end speed. Increasing the tooth count will do the opposite.

    • 4

      Attach the smaller sprocket to the sprocket hub, re-attach the drive chain and secure the rear wheel to the axle once again.

    Reducing The Weight

    • 5

      Replace the stock handlebars with an aftermarket lightweight alloy, by unbolting the bars from the front steering pillar. You'll need to remove the clutch and brake levers along with the throttle, starter and choke assemblies, reattaching them to the new handlebars.

    • 6

      Remove the front headlight assembly. Note that this is only recommended for race vehicles that will not have a need for night navigation.

    • 7

      Swap the front A-arm suspension components with a light-weight, high performance aftermarket set. This will require the removal of the front tires and disconnection of the upper and lower control arms, shocks and wheel hubs.

    Boosting Engine Performance

    • 8

      Swap the stock tail pipe for an aftermarket "slip-on" pipe that reduces resistance and increases top-end horsepower. You may also elect to swap the entire pipe assembly to the header, which is a "bolt on" upgrade that will require a tune up.

    • 9

      Replace the stock carburetor needles, jets and reeds with a high performance carburetor kit, which will increase air/ fuel flow boosting engine output. Having the carburetor polished will reduce air drag and allow the engine to breathe better, which will result in increased torque and horsepower. Along with an upgraded carburetor, replace the air filter with a filter designed for increased air flow. More air equals more power.

    • 10

      Replace the cam, pistons and valves with a high performance engine kit. Because of the complexity of this task, your local Kawasaki dealer or engine shop should complete this upgrade. If you're looking for a faster top speed without loosing torque, this will be the ideal upgrade to perform.