Saw this post due to my current situation and hope to find some answers. I have a cousin whose craftsman T210 started having starting issues. I brought it home and started to diagnose it. Everything pointed to bad ACR but the main thing that made me think of that was when you'd turn over the engine and it would stop at the compression stroke. Mower battery was bad (12v when key off then dropped to 6v when key was on, engine off) so I used my battery off my zero turn and it would turn over but eventually get weak ( i assume due to how long it was cranking) and stop at the compression stroke. Saw some YouTube videos that said if you have a bad ACR, cover the intake port and that will get you by, so I did that and the mower turned over fine and started. So since I work for a shop, I took the engine with me and tore it apart to verify the issue, but I did adjust the valves to make sure I wasn't forgetting anything. After removing closure plate (bucket engine) I removed the ACR and everything was fine. ACR moved freely and spring was still there. My cousin's husband did mention that when he tried to use the mower last time, he saw sparks come from the starter or in that area and when I had the engine on the mower, turning it over sounds like crap, like something was holding it back from turning it over smoothly. Engine model is KS40-3011, serial number 4904909253.
I still have the engine apart but am going to put it back together soon.