Michael; if your engine and carb are basically stock, check that your spark plugs, wires, condenser, coil and points are in good shape and that the timing, spark plug gap and points gap are within factory recommended settings. That is also a common problem with dual carbs when the engine isn't set up properly and can be attributed to improperly set accelerator pump, timing and/or incorrectly sized main and idle jets for the application. If I've missed something, please feel free to jump in.....