while riding the bike at a consistent140kph for thirty miles approx ,there was a sudden change of tone from the engine,initialy i thought i was to change my fuel tap to reserve -so i did -no difference even when i filled it with petrol.it had a colder front cylinder than the back one when i finished my journey and the plug was fouled with black carbon.i changed the plugs and cleaned the carb .i got only a slight power increase .it is still running horrible .i wonder is the cdi box damaged[it and the connections are not damp or wet.