My 51 plate sprint st, 45k miles, has a strange habbit. Once warm, when I pull up to lights the engine revs to about 2200 and wont come down, as soon as I put it into neutral (light comes on) the engine drops to the 1200 it supposed to do? Any ideas. It is mapped, but it does the same what ever map I put into it. When its up at speed, absolutely no issues at all, just at tickover! a bit rubbish at low revs pull away, but that was like that before I mapped it. Werx pipe and K&N filter fitted. It was running smooth as silk all through the good weather last year, but cold and damp its a pain!
How does it act when cold? Is the bike struggling a little when it's warm and doing this? I only ask because often weird idle behaviour is a sensor not working and the ECU assuming the engine is cold and the air temperature is very low, so ramps up the choke, which produces higher idle speeds. Could be a sensor on it's way out rather than being dead. Could also be something around the throttle, although the behaviour in neutral throws that off. It could be your mapping has done something else that is causing it, I assume when it was working fine you had the mapping installed then? It might need someone with a laptop able to read any errors the ecu is reporting to pin down the problem.
