Re: Johnson AD-12 mystery

[Don]

Trying to follow this, but fear any conclusions I made might be based in my inaccurate interpretation of what you have told us.
I guess I would begin with the flywheel hitting/rubbing situation. Like Frank says, we realize you were not banging/prying on the flywheel, but the past owners surely might have. You seem to suspect that the flywheel is going down to far when torqued in place, which is what would occur if it has been over tightened in the past. Can you see just what part of the flywheel is hitting just what part of the mag plate? Again, you seem to indicate the flywheel is not hitting the coil(s). The mag plate itself could be bent could be bent from improper installation, or perhaps someone prying up on it during previous repairs. You indicate that the mag plate and support plate is installed properly. Another possibility is that the brass retaining ring is bent/distorted, or not installed properly. Again, we don’t know what type of repairs were made in the past. I agree with you, a bent crank seems unlikely, but surely possible. How about the crank/flywheel tapers? If the key was sheared in the past, there may be aluminum transfer onto the crank which is causing the flywheel not to seat properly onto the crank. I would definitely use a little fine lapping compound to check the mating surfaces. But, you need to be very careful on this engine because there is no upper crankshaft seal. So, you will need to carefully tape off the crank/block area to cover up the oil deflector area.
After doing some investigative work to determine just what part of the flywheel is hitting just what part of the mag plate, I would probably find a used flywheel/mag plate and brass retainer just to eliminate these issues and to ensure proper coil to flwyeel air gap. I’m assuming you are not located near me in Rhode Island, of else I would offer these used items to you.
Once interference/air gap issues have been resolved, you can move on to faulty internals such as coils/points/condensers/wires.
The only other issue not to be ignored is the point cam. I don’t think it can be installed upside down, but who knows. Perhaps the cam is worn/gouged/rusted causing inaccurate point operation.
Please forgive me if I have misunderstood any of your posts, don’t be afraid to correct me. But, at this point, I would sure start right at the beginning, and not make any assumptions. Again, we don’t know just what was done to this poor engine in the past, so we have to consider all pieces/parts and past procedures as suspect.