Briggs & Stratton 31C707-3005-G5 500cc 17.5 Gross HP Engine with 1-Inch X 3-5/32-Inch Length Crankshaft Tapped 7-16-20  (Older Model) Cast iron cylinder sleeve and dual element air filter for extended engine life Float carburetor for consistent, easy starting Pantented linear balancing system provides smoother performance CARB Compliant CARB Compliant