Small Engines (Lawn Mowers, etc.): kohler 17.5 hp lawnmower engine, fly wheel, lawnmower engine

Question
QUESTION: I have a kohler 17.5 hp lawnmower engine it was running fine then it made a loud pop and stopped running then wouldnt start. I took the fly wheel off and replaced the keyway the mower still wont start. What else can i check and how? Thank you in advance

ANSWER: Have you tried rotating the engine by hand? Does the engine spin freely? If so, try removing the spark plug, insert a screwdriver and rotate to see if the piston is moving, if it isn't, the rod is brokent and it's not worth fixing. Let me know if it could be something else.

---------- FOLLOW-UP ----------

QUESTION: I have dome what you suggested and I did not feel anything. However when I took the valve cover off and turned it by hand the valves still move as they should. With a broken rod would the valves still move? Thank you

Answer
Yes, the valves would still move as usual, the camshaft gear is driven by the gear on the crankshaft. Try pulling the spark plug and putting a long screwdriver in the hole and try pushing the piston. If you can push the piston and the crankshaft isn't moving then the rod is broken.