My good friend and a Mooney M20J old timer has an issue with his IO360 . His engine was running rough due to low (zero) compression on one cylinder after take off from KSBP. It appears that one of the intake valves is cupped and not seating properly. Please see the pic. A sticky intake valve is the primary suspect.
Has anyone seen this and has any idea what could cause it? The mechanic pulled the cylinder today and will send it out for repair. The main question is what could cause this other than a sticky valve?