"Bob, have a few test numbers
"Bob, have a few test numbers for ya -
The 71, 4 horse had a Thunderbolt 2 ignition (with points). My parts lists and my manual are giving me slightly different descriptions of the ignition on the 71 - it was a change-over year for the ignitions themself, but think I have the right one.
The Stator on this has both a low and high speed coil plus a capacitor (condenser) and is tested as a complete system.
Stator - red (+) to the green stator lead (which is actually the feed from the capacitor), black to ground - ohm scale rx1000 - no continuity
Reverse the leads - ohm scale - rx1000 - should read 20-50 (20,000-50,0000 ohms)
Coil, positive to positive (coil), negative to negative (coil) - total continuity (some minimal resistance is acceptable but no firm value) - basically want an un-interupted circuit.
Points - no test - recommended to be changed every 500 hours of run time - gap is .020"
This system works kinda backwards to alot of breaker systems. With this one the current flows to the plug when the points "close" releasing approx 1000 volts from the capacitor (which rectifies and stores the power produced by the ignition coils).
This can cause significant pitting/deterioration of the points. It is NOT an issue unless they degrade to the point where you can no longer clean them and set the correct gap.
Most parts are long discontinued for this model so you may have to check some place like
www.oldmercs.com for what you are after should the need arise..."