Fleetwin…thanks for comments. I was nervous about removing the reed plate,but, on the chance that the top cylinder valve wasn’t closing properly, I swapped the bottom cylinder valve with the top: no change…the top still wasn’t igniting.
The motor ran fine last summer, until late in the season when it became hard to start and would run only with the choke open…and poorly then. Carb was rebuilt over the winter.
I have used the inline spark tester, running at both idle and as high a speed as I can get it in a barrel. The spark seems to be the same on both cylinders.
As I mentioned in my initial post, there was some oil under the magneto plate which I cleaned before replacing points. Would a bad upper seal present these symptoms?
Thanks again