I've tried to and seems to workNo it won't work, if you are modifying a magneto then you can just use the points to brake the low voltage supply to the coil but you will need a 12v battery to supply it.
I have a dead Lucas magneto on my 1950's rotavator, the cost of rebuilding the magneto is more than its worth so I'm going to fit a battery and coil to it.
@Rig Pig I've got success
I've discovered where was the problem
Essentially to have a good spark I put a grounding wire to connect the primary coil core to the ignition coil core .
I've got a good ¾" long spark 19mm
After this success I've put the modified magneto in place , sprayed some easy start fluid into the carb intake , pulled the recoil and it did bang , and a second time
No gasoline into the carb
But it's alive now I have to figure out how to make a fuel tank and then I can use it for a project