Engine stalls at idle: where to start looking

A bike that pulls fine on the move but dies at the traffic light rarely has a sudden big failure: the cause is usually simple and cheap. In November, when a cold engine is at its fussiest, it shows up most.

• Check the spark plugs: fouling, oil or heavily worn electrodes cause misfires at low revs.
• Inspect the air filter: a clogged or wet filter throws the mixture off and upsets the idle.
• Look over the intake boots and vacuum hoses: a crack or a loose clamp sucks in extra air and the revs hunt.
• Check the throttle cable: it should move freely with a small amount of play at the grip, or the throttle won't close properly.
• After warm-up, see whether the engine holds its idle. If it stalls only when cold, the cause may be in the fuel system or the sensors.
• Fuel system and electrics: if the steps above change nothing, go to a workshop. Opening up the fuel line is risky for a beginner.