Thanks for your help guys,richening the mixture has no effect,have inspected all the gears in clutch casing,tried a clutch off another bike,still no difference.Have recently fitted new kickstart gear and idler gear as kickstart gear broke,but it had this bloody noise before and after doing this.I've been thinking,does the gear oil on this bike also oil the main bearings,if so could some particles from the damaged idler gear got to the mains and lunched them?It vibrates more than it used to as well.fantastic bike when its right though.