a misfire is a symptom of a malfunctionaing igntion system be ait a spark plug or a cdi that is at fault ,also a misfire will sound like someone is turning the igntion switch on and off quicky as the spark would be disapearing and re-appearing.so unledd its doing that its not your problem,it sounds to me like you either hav a slow running jet problem or the engine is low on compression.does it 'misfire' if you rev the engine up?
adam bike doctor, March 2010
