Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
This is the older flat had engine, and may be a valve open. Can be stuck or damaged. The valve springs and lifters are behind the carburetor/exhaust , and are under the vent cover, where the hose to the air inlet goes to. # 8 in the parts list below.
Did you check the valve clearance? .006 inch is ideal, but if it has only clearance it will work, but zero will not! Valve not beening closed, would cause the fuel to blow out carburetor.
Sure, but sounds like a valve is open, or not seating.