Water down the carb throat is an old trick,and it works,steam cleans the ports,valves and combustion chambers,Now wer'e not talkin large amounts of water(that will hydraulic the motor and bend rods) just get her good and hot,set the idle about 2500 rpm and trickle about a qt. to a 1/2 gallon down the carb throat, beware that if'n ya got cats that they will turn cherry red...