New thread to make the topic a little easier to find in the future. As some of you know I've been trying to understand and fix the idle problem in this Thread. Short story, discovered cylinder 2 steals fuel from cylinder 1 at idle via the IAC pipe that links both throttle bodies. This can cause rough running, fouled plugs and much frustration! As I have an aftermarket ECU fitted and the diagnostic tools to monitor the AFR in both cylinders simultaneously I was able to rule out any problem with the programming of the ECU. I wasn't planning on going much further as I could mitigate the problem somewhat with changes to the ECU. But it still bugged me, so yesterday I pulled the throttle bodies off. Bit of a mess oil everywhere, I put this down to a remnant of the bad old days before Norton got a workable solution to the oil in the airbox problem. I then took the throttle bodies to an engineering shop and had them machine a suitable plug. Reinstalled the throttle bodies and without the IAC assembly to contol the idle I opened the throttle butterflies a touch using the throttle position screw. The result was pretty spectacular, no backfiring, hesistancy etc. It idled PERFECTLY - you could hear it with your ears and you could can see it on the oxygen sensor display. Video here. Next step is to see if I can add the IAC valve back so I don't need to worry about holding the throttle open when cold. I have an idea as to how to achieve this. I couldn't believe the difference - best way to describe the sound of the engine would be happy! If you have a stock bike and want to try this then you may need to keep the IAC valve electrically connected in case it throws an error. You must block the balance pipe between the throttle bodies NOT the IAC pipe that leads to it.