I have just had the same problem with my Honda foresight 250 cuts out at roundabouts and junctions but, not all the time. I called out the RAC and was told by the person who attended said it was the idle jet which would explain the problem. The bike was started opening the throttle wide open and eventually coughed into life., He adjusted the throttle stop by tightening it up and increasing the tick over. I have used a can of carburettor cleaner through the air intake, I was hoping that this would fix it for good, and the bike cut out in the same way. I’m not sure what to do now?