ok, so i managed some garage time today.
first, disconnected the (+) lead from the starter. thumbed the switch, solenoid clicked once
and then once more upon release, as it should.
measured the voltage: fine.
connected everything back up: solenoid goes "tzzzzzzt"
pulled the starter out, hooked up directly to a battery: spins fine.
put it back into engine, again attached the battery directly, and it cranked the engine effortlessly.
put everything back together again and what do you know - turned over several times, a few puffs and coughs and start it did.
so, problem solved... itself.
