How to Troubleshoot Motorcycle Starting Systemsby TJ Hinton
Motorcycle starting systems are fairly simple, and have actually changed little over the years. You can systematically check your starting system using a multimeter, common hand tools and your hearing. Since the most of the system components make some sort of noise, sound diagnostics work particularly well for chasing starting problems. If you disconnect the battery, remember: negative cable off first and on last.
Start investigating the problem with the components that are easiest to check. Ensure that your battery is fully charged and showing from 12.5 to 13.6 volts on a multimeter set to “Voltage DC.” Inspect the battery post-to-terminal connections and clean them, using a wire brush or terminal tool, if corrosion is evident. Make sure that the battery terminal connections are tight and secure. Check the condition of any fuses or fusible links in the starter circuit, and replace them as necessary. Check the electrical connections at the ignition switch for corrosion and tightness.
Turn the ignition switch and the kill switch to the “Run” position. Hit the starter button and listen. You should hear the click of the starter relay and the clunk of the starter solenoid. If you hear no click then the ignition switch, relay, power to the relay or a bad connection at the primary side of the relay is likely the problem. If you hear a click but no clunk, then there may be a bad connection at the secondary side of the relay, bad connection at the solenoid, bad connection at the starter or a bad solenoid. If you hear the solenoid clunk, then you know that the solenoid primary side and everything else in the circuit is working up to that point.
You can test the secondary side of the solenoid by isolating the secondary from battery power, then hitting the starter button with a multimeter on the secondary posts set to “Continuity” or “Resistance.” You should have continuity, with low resistance, when the starter button is depressed, and an open circuit when you release it. If the solenoid is good, the next thing to check is the starter itself. Remove the starter and inspect the drive gear for damage that could indicate a misalignment with the ring gear, and replace. Bench-test the starter by briefly connecting it to a12-volt power supply while firmly holding the starter down on a bench. Replace the starter if it is bad, and ensure that you follow your manufacturer's instructions for aligning and reinstalling the starter.
If you have not isolated the problem by now, it probably is within the safety devices. Most modern bikes come with these devices to prevent a rider from starting the bike in an unsafe condition, such as in gear, with the clutch engaged or with the support stand in the down position. If one of these switches is bad or simply disconnected, then it can prevent the starter circuit from operating. Check your bike for these devices and repair them as necessary. Some bikes also have a feature that will disable the starter circuit if your brake fluid is low, so check your reservoir and the sensor as well. If the bike still won't start, it must be a problem with the associated wiring. Check for any skinned or burned wires and repair as necessary.
TJ Hinton trained as an auto mechanic at Mississippi Gulf Coast Community College and then later graduated from MMI as a certified motorcycle mechanic . He's also worked for 20+ years in home construction, remodeling and repair. His articles appear on InternetAutoGuide.com and TopSpeed.com.