[Rev]

Or could be the opposite problem (not enough accelerator pump shot) causing a lean bog when you give it the gas. Either way, it's most likely a carburetor problem. Rebuild it yourself or buy a quality rebuilt carb and install it. Could be as simple as a ripped diaphram in the accelerator pump (easy to fix).

Look down the carb bore with the engine off. Operate the carb linkage by hand to WOT. There should be a good steady stream of gas from the accerator pump nozzles (shooters) near the top of the carb. If not, then you know where the problem lies.

Rev