When a motorcycle starts with push/bump start but not with the starter motor or kick start, it indicates a problem with the electric starter system or kick start mechanism. Push/bump starting allows the motorcycle's engine to turn over and start using the momentum generated by the movement of the bike.
Here's how push/bump starting works:
Engage the clutch: Pull in the clutch lever to disengage the clutch. This allows the rear wheel to rotate freely without transmitting power to the engine.
Build up momentum: Push the motorcycle to gain a significant amount of forward momentum. This can be done by running alongside the bike or having someone push it for you.
Pop the clutch: Once you have built up enough speed, release the clutch lever while still maintaining forward momentum. Releasing the clutch rapidly transfers power from the rotating rear wheel to the engine's transmission, which in turn rotates the engine's crankshaft.
Ignition and fuel delivery: As the engine rotates, the ignition system fires the spark plugs, and the fuel delivery system supplies fuel to the engine. The combustion process begins, and if everything is functioning properly, the engine should start running.
When push/bump starting, the rotating motion of the engine components, combined with the spark and fuel, helps initiate the combustion process and get the engine running. However, it's important to note that push/bump starting is not a long-term solution and should only be used as a temporary measure to get the motorcycle started. It is recommended to have the electrical starter system or kick start mechanism inspected and repaired by a qualified mechanic to ensure proper starting functionality.