Hello and thanks in advance for any advice.Inherited low hour mower after it sat for couple of years.Engine will not make complete revolution.Stops in bind around 300 degrees both directions.Evidently at time for exhaust push rod actuation as it never moves.Exhaust valve moves by hand and intake works normally.Search finds mentions of object introduced to intake.Carb. was left off for some time,but i see no evidence of anything inside.Belts are not stuck.Any advice toward logical diagnosis appreciated.