Another thing to note is that this older version of the engine doesn't have o-rings but has rubber/neoprene oil seals on both ends of the crankshaft to seal the crank case, they are like the o-rings in the respect they need to work.
Maybe one of those rubber/neoprene oil seals has partially failed allowing an air leak to develop. This would bring on the same symptoms as a failed starter 'O' ring failure in the later model 'Power-Torque'.
