Will do. But I'm pretty certain I've got the order right. Rechecked this a bunch of times. In fact, with the valve cover off I know that cylinder 4 contact and wire match with the cylinder. I'm pretty certain the ignition is all set right.

I'm beginning to think it's a float valve problem on that carb. You might remember that I'd found fuel pooled on the head at the aft carb, which sounds like a float overflow. And if the valve is stuck open, that would flood cylinders 3 and 4. Those plugs have been mighty wet when I've pulled them. And a carb problem might account for the rich and lousy running (bad idle and backfiring when cold) that prompted the tune-up in the first place.

Rhys has suggested plugging the fuel feed line to the carb and seeing whether the cylinders kick in as the mixture normalizes. At any rate, I'll pull off the float covers tonight, work permitting, and inspect and clean the floats and give this a crack.

This sound plausible to you?

Steve M.