How to Change the Front Sprocket on a Kawasaki 300R

The KLX300R is a 292 cc single-cylinder off-road motorcycle produced by Kawasaki from 1997 to 2007. The KLX300R was intended for enduro-style off-road racing. which required machines to have the off-road capabilities of a dirt bike with some road-going components, including a headlight and a more flexible suspension setup. Since the motorcycle was created as a competitive machine, many KLX300R owners change the engine's front sprocket in favor of a smaller sprocket to increase torque at low rpm. The process is fairly straightforward because of the easily-accessible location of the sprocket and Kawasaki's use of snail-shaped chain adjusters at the rear wheel.

Things You'll Need

• Pliers
• Socket, 36 mm
• Socket wrench
• Socket, 10 mm
• External snap ring pliers
• Aerosol parts cleaning solution
• Shop towel
• Molybdenum-based grease
• Sprocket circlip
• Torque wrench
• Ruler

Instructions

1. Park the KLX300R on its side stand and let the engine cool for a minimum of 30 minutes.

2. Remove the cotter pin from the right end of the rear axle using pliers. Loosen the rear axle nut using a 36 mm socket and a socket wrench. Rotate the chain adjusters on both sides of the swingarm forward by hand to loosen the drive chain.

3. Remove the front sprocket cover from the left side of the engine, near the left frame rail, using a 10 mm socket. Remove the sprocket circlip from the channel cut into the end of the transmission output shaft, using external snap ring pliers. Lift the drive chain off the sprocket teeth, then pull the sprocket off the output shaft.

4. Clean the transmission output shaft splines with an aerosol parts cleaning solution, then wipe dry with a shop towel. Coat the transmission output shaft with molybdenum-based grease.

5. Slide the new sprocket onto the transmission output shaft, then lie the drive chain over the sprocket teeth. Snap a new circlip into the channel at the end of the transmission output shaft. Reinstall the sprocket cover onto the engine, then tighten the cover bolts to 7.6 foot-pounds using a torque wrench.

6. Rotate the chain adjusters on both sides of the swingarm backward, then loosely tighten the rear axle nut. Check that both adjusters are properly aligned with the corresponding notches on both sides of the swingarm.

7. Place a ruler against the top of the swingarm and the upper strand of the drive chain. Lift the center portion of the chain and measure the distance the chain moves, using the ruler. Ideally, the chain should move between 2.15 to 2.55 inches. Evenly rotate both chain adjusters -- either forward to loosen the chain or backward to tighten the chain, if the chain slack measurement is not within the 2.15- to 2.55-inch specification.

8. Tighten the rear axle nut to 72 foot-pounds. Push a cotter pin into the hole at the tip of the rear axle. Bend the cotter pin's legs up and around the cotter pin.

References

• Kawasaki KLX300R Motorcycle Service Manual Supplement; Kawasaki Heavy Industries
• Kawasaki KLX250R Motorcycle Service Manual; Kawasaki Heavy Industries