Motorcycle starters consist of a 12V DC motor, solenoid and starter gear with an overrunning (sprag) clutch. The starter motor runs on high-amperage battery voltage and generates significant heat when operated. This heat can lead to insulation breakdown (IB) within the motor, causing low starting power. Sprag clutches, which disengage the starter and the engine once the engine RPM exceeds the starter RPM, can wear out and no longer engage. Solenoids are prone to arcing internally when actuated. This arcing will eventually lead to a reduction in the power being supplied to the starter motor, causing weak starts.
Remove the battery's negative cable from the battery with a 10mm wrench then stow the cable where the wire cannot touch the battery terminal. Remove the large negative cable from the starter/solenoid. Remove the large positive cable from the solenoid. Remove the small wires from the solenoid.
Remove the bolts holding the starter housing to the engine block. Slide the starter out of the block until it comes free. Inspect the starter gears in the starter and the engine block for wear, damage or missing teeth. Severely worn, broken or rounded teeth on the engine gear indicates an alignment or wear issue with the starter, and the gear must be replaced at the same time as the starter.
Insert the new starter into the engine block. Install and torque the starter bolts to factory specifications for your year, make and model of bike. Follow the factory recommendations for aligning the starter gears. Misaligned starter gears may lead to low starter power (starter grunt) and premature gear wear.
Reconnect all cables and wires leading to the starter/solenoid and torque to factory specifications for your year, make and model of bike. Reconnect the battery negative cable and tighten firmly with a 10mm wrench.
Test-start the bike and listen for starter grunt and excessive gear noise, indicating a misalignment. Repeat the procedure of removing the starter and reinstalling it if it is misaligned.
Listen to the bike when you try to start it. A clicking sound indicates that the starter relay is operating but not the solenoid. A clunking sound indicates that the relay and the primary side of the solenoid are working, but there is a power loss in the secondary side of the solenoid (bad solenoid) or a power loss in the starter caused by IB.
Exercise caution when removing the old starter. Starters are full of copper windings and may be heavier and hotter than they appear.