Very cool!
First wav file - your starter bearings need lube or your brushes and armature need dressing.
Second wave file - You can actually hear the sound of air displacing in the crankcase between cylinders as pistons reciprocate. Would be much better with a PVC system vented to the intake manifold.
Third wave file - is this after a thorough warm up?
Your microphone would make a good internet diagnostic tool!
