The problem is that the carb is too lean. The cause could be one of a number of things.
First thing to check is the idle mixture. Sometimes turning it out a 1/4 turn will correct the problem. If this doesn't help, inspect the intake system for leaks. Extra air drawn in after the carburetor will artificially enrich the mixture at low speeds but be insignificant at high speeds. If that doesn't do it, the carb may either need cleaning, or the float may be set too low. This is more common than it should be due to the propensity for the needle valve to leak. In a mistaken attempt to stop the leak, the level gets set way to low instead. It looks good until the engine starts drawing fuel and the level drops to the "run time" setting. Lastly, if it is really cold and the pressure is high, it may stumble a little even though everything else is correct. Adding carb heat will enrich the mixture enough to get over it. John Cooper Skyport Services www.skyportservices.net
