TOPIC: Johnson AD-12 - no spark - need gurus!!

I'm stumped.

Pick up a nice looking 1958 AD-12 7.5 horse for the girlfriend to work on as a project. No spark, but seemed to have good compression and turns freely. Popped the top the other day and cleaned everything up but still no spark on reassemble.

Gave it another shot tonight after pulling some coils off the siezed 57 Big Twin. got it back together and I had spark on the top cylinder, but none on the bottom. I will spare you the comedy of errors that ensued from there with troubleshooting, but by the end of tonight it has 2 new coils that I had sitting on the shelf. Still only have spark on the top!!!

So here's what I have:

2 new coils - only one gets spark to the plug
I checked the wire and it has continuity to the plug fitting
Points seem ok, and I cleaned them up a little
Polished the inside of the flywheel during the first go round.

Would a bad condensor kill the spark? Is there a way to test the condensor with a meter? I can go back to the Big Twin for a condensor from there, but who knows if that is any good. Should I swap out the points? The side with no spark doesn't look any worse than the side with spark.

Is there anything that I missed? The only thing that I can think of is that the plug wire might be shorting out somewhere, but it would need to be a dead short. The plug that is firing has a VERY strong spark, so I would think that even it is was shorting I would hear the arc or at least get a weak spark.

Throw me a lifeline!!!! I had that thing together and apart too many times tonight. I did fire it up on one cylinder with a shot of carb cleaner. Fired right away. Very frustrating!!

Condensers can be bad, since you have some spares might as well swap one in.

I've had bad points where the 2 halves had leakage to ground. Clean up a spare set of points to bare metal, then polish with crocus cloth. Degrease the contacts and set to a loose .020", then see what happens.

It's certainly possible to have a bad plug wire; where they route around the bottom of the mag plate you've got a possibility of a breach in the insulation.

If you get no traction from points/condenser, I'd certainly inspect the entire wire for any breaks.

Hopefully the new coil is good! You never know what evil lurks in the heart of new parts!

Had an appt this morning at 9, so I got up a little early and:

1 - Swapped in a different set of points
2 - Swapped in a different condensor

Put it back together with the top on - getting pretty good at it with all the practice in the last 24 hours! No Spark!!!!!

Sending the girlfriend to the local marine parts store to get the impeller that she needs along with a length of plug wire. If I get ambitious I will swap coils side to side, but I don't think the coil is the issue.

If that doesn't fix it, I will progress to 5 gallons of diesel and a match......

Well, you don't have to immolate the Evil Johnrude just yet - Carl Kiekhaefer already did that for you years ago when he hoisted an Evil Johnrude V4 by its Petard and lit a bonfire underneath!!

Sure does point to a bad plug wire, or maybe a bad new coil. Wouldn't be the first time a new part was no good!

BTW be sure to get the coils properly spaced on the mag. The armature should be flush with the flat machined surface of the mag, on the O.D. OMC had a special spacer ring that slipped over those machined parts, then the coil would be positioned right up to the ring for proper spacing. But as long as the coil's armature is flush, you're good to go.

Keep on pluggin' away, you'll get the Evil Johnrude beaten into submission yet!

BTW, be sure to run that 7.5 on 24:1 pre-mix, they have babbit bearings on the crank & rods and cannot be run 50:1.

Love the picture of Crazy Carl! I understand his feeling in wanting to burn one up again.

New wire, different point and condensor set. No spark. Tested everything and then swapped condensors from the side that was working to the other side. Had spark on the good side momentarily, and than that side died!!!!

Good thing I don't have any diesel!!!

I have a bunch of condensors for a parts auction earlier this year. I will try some new ones, and potentially swap out the coils again.

Not a very happy camper.

That can be quite irritating, almost time to hoist up the Evil Johnrude!

But before doing that, check out this very informative writeup on condensers:

mgaguru.com/mgtech/ignition/ig129.htm

Very few of us have an expensive tester around, but most will likely have a volts/ohmmeter and he shows you how to do some testing using that. Good Stuff!

p.s. you can compare meter readings on your known-good condenser and compare those to all your other used ones, that should tell you something!

Good stuff Ed! I will take a look at them this week and see what I get.

BTW - looked at my condensor stash and all of them are Merc / Quicksilver condensors that want to lay on their side per the bracket. Guess I go back to canibalization of the dead OMCs in the garage.

May be obvious, BUT, you sure that the leads from the coils are going to the correct sides? This can result in no spark on either side. Don't ask me how I know this...

Pretty sure that we have it wired up correctly with hot and cold wires. Does it matter which bolt the ground is hooked to? # choices on each coil, I just was having it go to the opposite side of the coil from the points, matching up what was there. Would it be better to ground to one of the bolts that goes through the coil and hooks it to the powerhead? Maybe that's my problem?!?! I will take a look at the manual

Update - just looked at the manual and I think that my wire routing might be correct. Two things that looking at the manual made me think of:

1 - I need to check to see how the coils are lined up in relation to the flywheel. I don't have the ring tool, but the manual mentions that you can use a straight edge in a pinch. Ed - you mentioned this before but I didn't know how to test. It could be that all I need to do is adjust the problem coil out a little more so that it is closer to the flywheel.

2 - What does the "wick" do for the armature? Excuse my ignorance, but if it helps with grounding that could be part of my problem too.

The manual shows how to hook up a condensor for testing, but doesn't go into how to test it - it just states replace.


Here's some good info: www.leeroysramblings.com/johnson_magneto.htm

The wick just holds the oil to lubricate the rubbing block. Has no function electrically, just reduced wear.

The system is quite simple. I would look for a pinched wire at this point. Each set of points fires each coil. The kill switch shorts both to ground.

Just a thought here. I didn't follow this from the beginning but does the motor have an over-rev safety on it. Could be that the vacuum is stuck and shorting out one of the points/coils as a safety measure. If it does just disconnect the wire from the switch or pull the vacuum hose and plug it.

Nope, the little Johnnies didn't have that vacuum switch or wiring that was found on the Big Twins.

And if you've ever run one of those Big Twins without the vacuum cut-off hooked up, you'll never forget it!!!

Fast revving motor Ed? Or just it just get going and want to keep going?

I had read about that vacuum switch in the front of the manual and was pretty happy until I saw it didn't apply to the 7.5!

As I was pulling parts off the Big Twin I saw the extra wire going to the points I was removing.

Didn't get a chance to test the positioning of the coil using the straight edge method. Didn't have time to fire up the laptop to follow the procedures. I did get the ohmmeter on the condensers, and pretty much verified that one of them is bad. The others that I tested seemed to follow the movement pattern described in the article Ed linked

What happens if the vacuum switch is disconnected? I had a 33 horse that would start running away at idle if you revved it a little too high and you would have to choke it out to slow it down. That was over 40 years ago so I don't remember if it had one of those on it or not.

The vacuum switch is a diaphragm that runs on vacuum in the crankcase. When vacuum is really high it closes the switch and shorts out one of the point/coil circuits. Mark if you switched that harness leave the black wire separate, if you ground it that will short out the point.
At least I think that is how it's supposed to work

Yup, they do like to run away without that vacuum safety switch. Quite scary!

Thanks guys. Right now the Big Twin is a siezed up parts donor. If it doesn't start cooperating I will part it out over the winter. Top is siezed, but LU is good to my knowledge.

Spent some time working on the AD-12 last night. It is getting pretty close to diesel and a match!!!!!!! Good thing it is the girlfriends project and not mine!

Swapped out condensors and we now have great spark on the top cylinder, but still none on the problem child bottom cylinder. Swapped out the coil, but then we were having issues with the flywheel hitting something on the armature. Haven't figured that out yet, but I had left the gf to work on it by herself so almost anything could be the issue as she is just learning how to work on these. I have an idea that we might have rotated the plate that the armature screws into by the driveshaft, and that could make things be off just enough to cause a clearance problem. I will try rotating it and seeing if that resolves the issue.

So much for an easy project!! Not a lot of money, but we have invested a bunch of time trying to track down the no spark issue!!

Not having much fun with this one. Still having spark issues, but now flywheel is hitting the armature plate. Looks like the plate is tight on the brass ring under the plate. No idea what is going on, very frustrated.

Any ideas what could be going on?

Mark, are you going to be home on Tuesday eve?
Monday is goblins visiting.
We'll take a look at the motor if that's ok.
Cal

Cal - any help would be great! Problem is that I am co- facilitating an estate planning seminar 6-8 on Tuesday. It is in GB, so I should be done around 830 or so barring a ton of questions.

I am starting to wonder if the top bearing is shot as there is a little play up and down. It is weird that it would just suddenly start to be a problem. I had the top off and on a bunch of times with no issues. It almost seems like a shim fell off, but I can't recall a shim on a flywheel. It is just bizarre that we suddenly have clearence issues.

Just mail me when you have time.

Will do!!

Here's a question - could the flywheel key have moved enough that it is causing the clearance issues? I compared the placement on the one on the AD-12 to one on the 15 horse. Definitely seems like it is not positioned the same on the 7.5. Wonder if that could be my problem? Maybe because the key angle has changed it is sliding too far down the crank and causing the clearance issues? Maybe that will help explain my spark issues too, as the clearance issue is on the same side as the spark issue.

I am ready for a simple solution with this one!!!

Top 3 pictures are from the problem child 7.5 hp, and the bottom 2 are for reference from a 15 horse that I am working on. Does it look like the key could be causing my issues??

7.5 AD-12



7.5 AD-12



7.5 AD-12

15 hp FD-10 for reference



15 hp FD-10 for reference

I have not had any luck in getting the flywheel key out of the crank. Any suggestions? I was going to try a torch to get things moving a little this weekend. It is really stuck in there.

GF is probably going to order a replacement key, so I am not too concerned with breaking this one. Problem is that I haven't had any luck getting it to budge.

Any suggestions that have worked for the JEGO gurus in the past?

I think it is past the danger of diesel and a match, but I need to get this one out of the garage as it has frustrated me long enough!!

Just a reminder but your motor needs a 16:1 fuel/oil mix. 24:1 was for the ten horse and larger motors with needle and roller bearings.