Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! Remove the valve cover and see if a valve has dropped into the cylinder. That seems to fit the symptom. If not valve, then you have connecting rod problem.
Remove the cover over the cylinder head and look for loose parts! There will be two rocker arms, and two sets of springs.
Damage will be evident.