[Rob Doe]

Check the main and cap jets for leaking at their bases. I had the same symptoms with a carb. I've got a long middle finger and could touch the two jets. They were dry at the top but wet at their bottoms. The gaskets were leaking. I got the black (plastic???) gaskets from Bratton's and the problem stopped.

I dropped the bottom half of the carb off and leveled it on the bench with wooden shims. Placed fuel in the fuel bowl and waited to see if the new gaskets leaked. They did not. The traditional red and gray did. Others have put a small amount of gasket sealer on the traditional ones to solve this type of leak.