Another Cub won't start question.

[Posco]

Hey, folks.

I was plowing snow with the Cub yesterday and it started to sputter and die out. It would run fine if I took the tractor out of gear and throttled it up, but it would sputter when I applied power when releasing the clutch. It ran fine for the better part of an hour and then the problem suddenly appeared.

I was reluctant to shut it down wondering if it would start today. It didn't. I put new plugs in it...Autolite 3116. I pulled the fuel line, there's good flow. Pulled the carb and cleaned the tube and jet.

I'm wondering about the distributor. It's been three or four years since I've messed with the points and am wondering if that might be the culprit.

Any suggestions?

[Posco]

I've forgotten how to get to the condenser and points. Do I have to take the entire mag body off the tractor to reach them?

[MiCarl]

Condenser and points are under the rotor. No need to pull the magneto off the tractor.

[Posco]

Thanks, Carl. It has been some time since I replaced them and I've only done it once.

[Jim Becker]

. . . Any suggestions?

Did you actually check for a spark? Based on the snow and ice in the picture, your problem may be moisture. Dry it and try it.

[Posco]

. . . Any suggestions?

Did you actually check for a spark? Based on the snow and ice in the picture, your problem may be moisture. Dry it and try it.

How should I go about that?

[Glen]

Hi,
You could use compressed air to dry the area. Wear your safety goggles when using the air.
You don't need to take the magneto off the engine to work on the points.
I use a chair, and sit next to the engine, and a good light.
The 1950 Cub owner's manual shows how to get to the points in the magneto, on page 30, if you have the owner's manual. They are under the plate held on with 3 screws, that the distributor cap is on. You need a short screwdriver for the screws.
The problem could also be the condenser or coil.

Below is the page from the 1950 owner's manual.

http://farmallcub.com/rudi_cub/www.clea ... e%2030.jpg

If you have to turn the engine slightly to get the points onto the high part of the cam, to set the gap, notice how much you turn the engine. The D shaped hole has to go on the shaft that drives the rotor, the right way.
You can lose the timing if you turn the engine with the plate off, and don't know which way it was turned.

[Jim Becker]

. . . Any suggestions?

Did you actually check for a spark? Based on the snow and ice in the picture, your problem may be moisture. Dry it and try it.

How should I go about that?

Take the wire off one spark plug. Hold it close to the engine block or head (about 1/4 inch away). Turn the ignition on and crank it over. You should see a blue spark that can jump at least 1/4". If the spark is yellow or won't jump 1/4", you have an ignition problem.

[Posco]

Thank you Glen and Jim. I found my copy of the owners manual. As I mentioned, it has been three or four years since I dug into the distributor. I had the mag reconditioned by Mainely Magnetos about that long ago. I asked him about replacing the coil then but he tested it and assured me it was fine. He had one on hand and could have easily sold me something I didn't need. He has a first-rate reputation. I supposed it could have since failed.

Hopefully I'll have a good report for you. Thanks again.

[Glen]

Hi,
Yes, the coil could have quit since the magneto was worked on. Some of them work when cold, and quit when warm.
If there is no spark, try this info.

Disconnect the wire for the ignition switch at the post on the side of the coil, and see if there is spark. The ignition switch can be grounding it.

People have posted on here that the insulation for the ignition switch wire post on the side of the magneto can crack, then the magneto shorts there, and there is no spark.
TM Tractor has new insulation.
I guess there are some magnetos that this insulation does not fit. It gives the magneto serial numbers of the ones it does fit in the listing. If you need one, look at the serial number stamped on the magneto and see if it is right. The serial numbers all start with J4, I think.

http://www.tmtractor.com/new/el/957fp.htm

If there is no spark, I would look at the points. If you file them, and the surfaces are shiny and flat, or you put in new ones now, and it still has no spark, you could put in a new condenser.
Then if it still has no spark, it's probably the coil. You probably know they are different than a regular coil. They have a square bar that goes through them, reuse the bar it has with the new coil.
Below is a listing at TM Tractor.

http://www.tmtractor.com/new/el/713fp.htm

[staninlowerAL]

Pay attention to the rotor and pinion gear position and timing marks. You can also loose correct timing if they get repositioned to a different gear mesh.

[Posco]

Disconnect the wire for the ignition switch at the post on the side of the coil, and see if there is spark. The ignition switch can be grounding it.

Hey, Glen

I disconnected that yesterday thinking that might be the problem but that wasn't it. I did not try to see if there was a spark there, never crossed my mind.

I was never much of one to want to fiddle with mechanics but when you buy one of these tractors, you're more or less forced to become your own mechanic. There's always something acting up on them. I enjoy working on it now and have conquered a lot of issues with the help of the manual and you folks offering your knowledge and advice. Collectively, you're the best there is.

It's twelve degrees out and I won't be working on it today but I'll keep you filled in when I find the problem.

Thanks for all of your folks help.

[Glen]

Hi,
What I wrote above meant check for spark at the spark plugs, or see if the magneto produces spark when running the starter, after disconnecting the grounding wire on the side of the magneto. I guess you already did that.

[staninlowerAL]

.......People have posted on here that the insulation for the ignition switch wire post on the side of the magneto can crack, then the magneto shorts there, and there is no spark......

Not to be reduntant but what Glen is referring to is the bakelite/plastic "insulator" that the post/stud passes through in the magneto housing that prevents the spark from grounding to the metal of the distributor housing. If you're handy with fabrication you can make one from a piece of plastic plumbing fitting or some other solid non conductor that fits into the hole. Another note is the "ignition switch" on a mag ignition is more correctly identified as an "ignition kill switch" for obvious reasons.

[Posco]

An addendum. I did manage to get the Cub running a couple of weeks back but ran into another problem today. It seems to coil in the mag has died. I can't get it to spark when I disconnect the ground wire and try to get it to arc.

It the interim between now and getting a J4 coil, how hard is it to externally wire a coil? I have one on hand.