Ok here's a mystery (to me...)

I've got an old lawnmower with a Briggs and Stratton 2 cylinder 4 cycle 
engine.

The starter motor lacks sufficient torque to start the engine. It 
sputtered and almost started one time, even so, but no success 
subsequent to that hopeful event.

I turned the flywheel by hand and it seems free enough.

I measured the voltage drop and there's about 1.2v total drop in the 
wiring between motor terminals and battery.

I put a new starter solenoid in.

I replaced the brush assembly in the starter motor.

I removed the armature and looked at it; it looks sound and I cleaned 
the armature contacts with contact cleaner.

The magnets look OK to my untrained eye. They are not loose and they are 
not cracked.

I read on the internet that someone had a similar problem, did all this 
stuff, and still had to replace the entire starter motor, which solved 
his problem.

I am about to drop $100.00 on a new starter motor.

Can anybody shed any light on the failure mode? Does this even make 
sense or am I missing something?

Thanks,
Mark
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