Why does a motorcycle stall at idle but has no ignition issues?
2 Answers
Reasons for motorcycle stalling at idle: Fuel line obstruction, faulty spark plug possibly malfunctioning, slightly narrow engine valve clearance, ignition wiring leakage due to high temperature, etc., requiring further inspection and repair. Carburetor mixture too lean: Since current motorcycles must meet Euro 2 standards upon leaving the factory, manufacturers often set the mixture ratio very lean to comply. However, the mixture ratio must be readjusted to normal before actual use, as proper mixture ratio ensures easier starting. Valves not fully broken in: Slight valve leakage makes it necessary to set the idle speed higher to prevent stalling. Overly tight valves with leakage can also cause starting difficulties. It's best to adjust the valve clearance. Additionally, inspect the fuel line and check the spark plug for any issues.
My old motorcycle has been doing the same thing lately—it stalls when I let off the throttle, but starts right up with a single kick. It's most likely a carburetor issue. Over time, impurities in the gasoline can clog the idle jet, or the throttle shaft may wear out and cause air leaks, messing up the air-fuel mixture. Cleaning the carburetor usually helps in such cases—don’t forget to check the float chamber needle valve too. If it still stalls after cleaning, it could be due to overly tight valve clearance or a worn-out trigger coil in the ignition system. Last time, my bike idled smoothly when cold but stalled when warmed up, and replacing the ignition coil fixed it. A dirty air filter can also cause idle stalling, especially after riding on dusty roads, so remember to check it.
