Johnson AD-12 mystery

[63lstrition]

Good point, but why would it be fine initially l and then turn into a problem? Are there shims on the crank or the flywheel?

[chris-p]

No shims.

As stated, very few reasons why the flywheel would hit the mag plate. Either that flywheel taper has been opened up as Frank said, or the mag plate is damaged. Is the brass ring in the center properly attached to the plate? Not cracked? Look underneath. You have to take it off anyways to inspect the support ring.

By the way, what a find regarding your girlfriend! Not only does she find a motor, she helps work on it!

My wife has a few "jobs" that I make her do, but she hates every minute of it lol

[david-bartlett]

Triton,

I have some pics of my AD11. Same motor, different year. In one pic you can see how the flywheel sets on the crank and its relative position to the magneto plate.

In the other pics my pencil points to the groove in the magneto plate and the corresponding edge of the flywheel that sits in this recess. It should not sit so low that it touches anywhere around the circumference as it turns.

I also have pics showing where the heel of the coil laminations rubbed on the magnet in the flywheel.

Hope these help rather than confuse. Hopefully you can use them to tell us where yours is rubbing.

---

Attachments:

[jerry-ahrens]

It sure sounds to me like your flywheel magnets are hitting on the coil laminates. In the pic, the screwdriver is pointed to the boss on the mag plate and to the edge of the coil laminates, or ”heels” as they are called. If the ends of the coil laminates are protruding past the edge of the boss, even a hair, they will stop the flywheel dead in it’s tracks. Check both coils carefully, and loosen the screws and align them evenly. Otherwise you can purchase the OMC special tool that makes this adjustment easily.
My suggestion is to purchase an OEM tune up kit for around 30 bucks or so, and replace both sets of points and both condensers and be done with it. Don’t waste time with Sierra points, they are junk. Set the points to .020 thousandths on the high side of the cam. The .020 feeler gauge should have a very slight drag while checking the gap and inserting it squarely, and carefully, at the same time. Once again there is a special timing pointer that is used with an ohm meter etc. to set the points, but using the feeler gauge method will work fine, if you do it correctly.

---

Attachments:

[jcrigan]

Overtorquing the flywheel nut will crack the ignition cam on the crankshaft. Impact wrenches will do that. Will then make the flywheel go lower on the crankshaft.

[fleetwin]

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.

[fleetwin]

Those pictures are surely worth a thousand of my words!

[63lstrition]

I am in a conference in Chicago right now and won’t be home to Green Bay until later tomorrow. I will try to post some pictures then to clarify. Until then:

– the flywheel is definitely hitting the mag plate – not the coils. It is hitting one of the cast round "knobs" just before the flywheel gets to the coils. Picture will help

– didn’t really check to see if the mag plate is warped. That could be causing the issues, but it doesn’t seem overtly wrong. I will need to figure out how to check for warping

– I have a few other plates to check fit – one from a 56 FD-10, one from a 57 Big Twin 35, and one from a 50-something parts motor. I would think I could check fit with one of those

– the cam appears not to be overly worn or cracked and fits snugly

– i will need to get my hands on it this weekend to check taper fit and the brass mounting rings

[garry-in-michigan]

Let me say I had a customer that had bought a tune up kit from me brought his motor in a week later. It was because He and his "Old mechanic" neighbor could not get the flywheel off. It seems his neighbor had been using a big screwdriver and hammer to remove the flywheel on his antique Johnson for 30 yeas and never had a problem. Evidence showed he was prying on the magneto base hard enough to push in the rear mount for the rewind starter and crack the water jacket when he hit the top of the crankshaft with the heavy hammer. Yes, he needed a new magneto base as well as several other parts.

Lesson – never under estimate the amount of damage a lack of knowledge may cause. That is why we are here to answer your questions. . . 😉

[mercuryman]

You need to check points with OHM meter , they must read 1 ohm or less. They can look great but still have resistance. You must unhook coil wire to check points. If you magnets are good it should spark.

[Author]

Posts