The jerking or abrupt movement experienced when starting a motorcycle's engine can have several possible causes. Here are a few common reasons for this behavior:
Choke position: Motorcycles often have a manual choke, which controls the air-fuel mixture during cold starts. If the choke is left on or partially engaged while starting a warm engine, it can result in a rich fuel mixture, causing the engine to jerk or sputter. Ensuring the choke is properly adjusted or fully disengaged when starting a warm engine can help alleviate this issue.
Throttle control: Inexperienced riders may inadvertently give too much throttle input when starting the motorcycle. Opening the throttle too quickly or excessively can cause a sudden surge of power, resulting in a jerky start. Gradually and smoothly applying throttle while releasing the clutch can help avoid this.
Clutch engagement: Improper clutch control is a common cause of jerky starts. Releasing the clutch too quickly or abruptly can result in the motorcycle lurching forward or stalling. It's important to gradually release the clutch lever while simultaneously giving throttle to achieve a smooth and controlled start.
Mechanical issues: Certain mechanical issues can also contribute to jerking during engine startup. Problems with the fuel system, such as clogged fuel injectors or a malfunctioning fuel pump, can affect the delivery of fuel and cause irregular engine behavior. Additionally, issues with the ignition system, such as faulty spark plugs or ignition timing, can lead to a rough start.
If the jerking issue persists or worsens despite employing proper starting techniques, it's recommended to have the motorcycle inspected by a qualified mechanic. They can diagnose any underlying mechanical problems and make the necessary repairs.