So here's the kicker for me. My mower is a Craftsman 21 HP 46" desk Model 917.288522 / Briggs & Stratton Enging Model # 331877 Type Number 2371-G1. I have an issue with my Craftsman B&G 21HP motor. It won't turn past 1/2 but if I have my Dad manually hand turn it past while I'm turning it over it will start. When we take out the spark plug the motor turns over like normal no problem. We first replaced the starter no luck. Then we replaced both intake / exhast valves and rods thinking that was the problem. Still no luck. Any and all suggestions / brainstorming will be welcome.