sounds like your exhaust valve needs adjusting. if it is closed and not opening to relieve compression pressure, it will be hard to pull. check the engine brake first. if the engine brake is working properly, take the valve cover off, remove the spark plug, turn the engine over and visually watch both valves open and close. If it is not in the valve train, while turning the engine over feel for play in the shift to rule out bearings. Have patience with the guys in this forem. They all want to help you, however some expect you to know more about troubleshooting than you do, and that comes from a lack of patience and compassion on their part ! I hope this helps you to fixing your problem, Pete's small engine repair