It is more than likely a bit of dirt/blockage in the carby. These carby's leave the factory borderline lean, to meet emission standards, it doesn't take much to block them and make them hunt. There are no adjustments on the carb and don't play around with the governor spring, it's most probably not the problem.As for the filter, clean and re-oil it but again a dirty/blocked filter will not cause it to hunt.
