What is the reason for the increase in idle speed after just adding gasoline to a motorcycle?
2 Answers
The added engine oil is a bit viscous, and when the engine is hot, the oil becomes thinner, reducing movement resistance, which leads to higher idle speed. Check the motorcycle's ignition system: Whether the fuel needle is worn. Whether the throttle cable's travel is too short. If the above are not issues, check if the ignition system is timed correctly, if the spark plug gap is appropriate, and if the spark plug is damaged. The impact of motorcycle idle speed being too low or too high on the vehicle: Whether the idle operation of the motorcycle and engine is good is one of the important indicators to measure the performance of the engine. If the engine idle speed is too high, it will increase fuel consumption, raise the engine operating temperature, accelerate wear, and produce impact sounds during gear shifting. Poor engine idle speed can be divided into three situations: no idle speed, excessively high idle speed, and unstable idle speed.
I've been repairing motorcycles for decades. It's quite common for a motorcycle's idle speed to increase right after refueling, mainly due to the temperature change of the newly added gasoline causing faster fuel evaporation, leading to a temporary imbalance in the air-fuel ratio. The engine's computer will attempt to compensate, but the idle speed may briefly rise. Another factor is the high alcohol content in gasoline, especially in blended fuels, which can result in incomplete combustion. My advice is not to rush riding it—let it idle for a while to stabilize. If the idle speed continues to rise, check if the air filter is clogged or if there are any impurities in the fuel line. Regular cleaning of these components can prevent issues and ensure safe riding.
