If the engine s running properly (no 'hunting' or black smoke), thee should be plenty of power for cutting anything up to about 8" long (assuming you are not trying to cut at 20MPH!).
For a start, sharpen the blade. A blunt blade TRIPLES the power requirement. If there ARE engine issues, change the carb diaphragm, and the spark plug. This will resolve 99% of problems with the B&S Classic range of engines.
phil_saunders(a)bigfoot.com
Phil Saunders
July 2009