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I will test the compression when I get it put back together.
I am sure it is the bottom cylinder because I have spark testers. Top is nice and consistent and strong while the bottom cuts out. I swap testers and the problem stays with the bottom cylinder. When the bottom does decide to fire it is nice and bright as well.
For the cut out switch, i disconnected from the switch itself. There is a nut on a stud the ignition wire connects to. I removed that.
A lower crank case seal can lead to poor ignition? How does that happen and how can I check? Upper crank seal I have replaced before and is easy to diagnose because of the mess it leaves on the magneto place
OK, disconnecting the lead from the vacuum switch is not the most accurate way of ruling out issues. The two black leads come out from under the flywheel and have those pesky “knife connections” with the chinese style torture tube sleeves. I would disconnect the leads at that point and tape them up to be sure they don’t short to ground. Again, something as simple as a lousy plug can cause the secondary voltage to drop enough so it won’t light the spark test light. Are you testing the ignition while the engine is running??
And no, a faulty lower crank seal would not cause the lower cylinder to lose spark.