old style magneto ..easy to repair.. no electronics  involved  🙂

check coil  resistance   primary wires   1-2 ohns     seconary HV pin to one primary should give  4-8 KILO ohms on the proper scale !!

try measuring plug boot to engine frame… check for  4-8 kohms  steady  …     do it on both  plug wires  to compare

if you  do change the coil .. take time  to replace the plug wires on both  coils  (use 7mm metallic  strand  wire no carbon stuff… local  mower or bike shops can sell a few feet of it )

clean points as a first step (150-200 grit and  acetone wipe after )    condenser may be bad  even if tested  OK  with a low  voltage  capacity meter.      easy to replace …

careful with new points if replaced..complaints have  shown up about bad fit.

if you   have  good coils,  new  points, condenser  wires  etc… should be good for  years  and years

lots of utubes on these