Anti-Backfire Valve

Start engine. Warm to normal operating temperature and run at idle. Disconnect anti-backfire valve hose at air cleaner. Place finger over end of hose and increase engine speed to 3000 RPM. Quickly release throttle and allow engine to return to idle. If vacuum is felt at end of hose, anti-backfire valve is functioning properly. If no vacuum is felt, replace anti-backfire valve.