Why does a motorcycle's idle speed drop and stall easily when warmed up?
2 Answers
Blocked fuel line causes it. Here is relevant information about car idling: Function of car idling: Idling is an operating condition of a car, referring to the engine running in neutral gear. The engine speed during idling is called idle speed. Idle speed can be adjusted by changing the throttle opening size, etc. Idling means the engine "produces power without doing work". When the engine is running, if the accelerator pedal is completely released, the engine is in idle condition. Causes of unstable idling: Direct causes refer to mechanical parts being dirty, worn, or incorrectly installed, leading to changes in cylinder power output, resulting in imbalance among cylinders and causing unstable engine idling. Indirect causes refer to abnormalities in the engine's electronic control system, causing poor combustion of the air-fuel mixture, making it difficult to balance cylinder power output, resulting in unstable engine idling.
Motorcycle idle speed drops when hot and stalls easily, I've encountered this several times. It could be that after the engine heats up, internal components expand, causing the idle speed motor or throttle to stick due to excessive carbon buildup, or the air-fuel mixture becomes too lean with insufficient fuel supply, leading to a drop in idle speed. Aging of the ignition system is also common; spark plugs may weaken in ignition capability under high temperatures, failing to produce sparks, making the engine prone to stalling at low speeds. If the air filter is clogged, reducing air intake, the idle speed will also become unstable. It's recommended to regularly clean the fuel injection system, replace the air filter and spark plugs to prevent many issues. Ensuring the engine cooling fan works properly is also crucial. On hot days, it's good practice to warm up the engine briefly before riding.
