I had not thought about a valve stuck open. I was more concerned with a valve stuck closed when I tried to turn the engine by hand. After I got the tractor home and offloaded I covered the exhaust stack (it, the gas tank and the radiator had all been left open for a few years) and poured the cylinders full of Marvel Mystery Oil. It took a couple of months for that to flow back to the crankcase. 

After I got the electrical rebuilt, I tried to crank it with no fuel, and the old plugs, old coil, old breaker and condenser, and got puffs. Then I replaced the rest of the electrical, hooked up the fuel system and tried again. I get a few puffs of smoke after the tractor has sat for a few days in between tinkering sessions. It will stop smoking after turning it a few times. That's why I thought not enough fuel getting there. 

I'm checking the compression in the morning and will go from there. I'll post back what I find.