How to Help Reduce Engine RPMs at Highway Speeds on a Kawasaki Vulcan 900


Although the Vulcan 900 is not the largest model in Kawasaki's Vulcan series of cruiser-style motorcycles, it is a capable short-range touring. But long stints on the highway can turn the vibration of the Vulcan's V-twin engine into a real pain in the saddle. Installing an aftermarket overdrive rear pulley, which has less teeth than the stock rear pulley, can reduce the engine's rpm at highway speeds. This in turn reduces the severity of the vibrations transmitted directly through your seat. As an added benefit, your Vulcan will enjoy a higher top speed, but it will lose some acceleration from a complete standstill.

Things You'll Need

  • 10, 12, 14 and 32 mm sockets
  • Socket wrench
  • Phillips screwdriver
  • Bungee cord
  • Pliers
  • Jack
  • 12 mm open-end wrench
  • Rear overdrive pulley
  • Torque wrench
  • Cotter pin
  • Park the motorcycle on its side stand and let it cool for at least 30 minutes.

  • Remove the exhaust pipe heat shields using a Phillips screwdriver. Remove the muffler mounting bolts, located behind and under both mufflers, using a 12 mm socket and a socket wrench. Remove the nuts securing the exhaust pipe holders to the engine cylinders using a 14 mm socket. Pull the exhaust pipes and mufflers away from the motorcycle.

  • Remove the cotter pin from the right side of the rear axle using pliers. Loosen the rear axle nut using a 32 mm socket and a breaker bar. Loosen the rear caliper bolts using a 14 mm socket. Place a jack under the frame rails below the engine and raise the rear wheel off of the ground.

  • Remove the rear caliper bolts and slide the caliper up and off of the rear brake rotor. Hang the caliper from the motorcycle's rear fender using a bungee cord. Remove the belt guard from the left side of the swingarm using a 10 mm socket.

  • Loosen the rear wheel adjuster lock nuts, using a 12 mm open-end wrench. Turn both wheel adjuster bolts counterclockwise four even turns to loosen the drive belt. Remove the rear axle nut, then pull the axle out from the left side of the swingarm. Pull the belt off of the rear pulley, then roll the rear wheel away from the motorcycle.

  • Remove the rear pulley from the rear wheel using a 14 mm socket. Slide the pulley off of the pulley coupling. Place the rear overdrive pulley onto the coupling's threaded mounting posts. Screw the pulley nuts into place, then tighten the nuts to 44 foot-pounds.

  • Roll the rear wheel into the swingarm and hook the drive belt over the rear overdrive pulley. Push the rear axle into place and loosely screw the axle nut into place. Turn the rear wheel adjuster bolts clockwise four even turns to tighten the drive belt. Tighten the wheel adjuster lock nuts against the swingarm. Tighten the rear axle nut to 79.7 foot-pounds. Push a cotter pin into the end of the rear axle, then bend the pin's legs around the axle using pliers.

  • Slide the rear brake caliper over the rear brake rotor. Screw the caliper mounting bolts into place, then tighten the bolts to 25 foot-pounds.

  • Reinstall the exhaust pipes and mufflers. Tighten the exhaust pipe holder nuts to 12 foot-pounds, then tighten the muffler mounting bolts to 18 foot-pounds. Reinstall the heat shields onto the exhaust pipes.

  • Lower the motorcycle onto its side stand.

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  • Kawasaki Vulcan 900 Classic Motorcycle Service Manual; Kawasaki Heavy Industries
  • Photo Credit Thinkstock/Comstock/Getty Images
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