Loosing Spark Again

[1 Dollar]

On my Unstyled John Deere A with a WICO X mag, I have blue spark when it is there, but whenever I can get it started it runs well 80% of the time and kind of hunts/misses the other times. I had it running for 15 minutes just now and 2 or 3 times it completely lost spark and acted like the ignition had been switched off. It would catch itself again and run smoothly, then miss a little, and keep repeating this.

Last time this happened you guys recommended moisture in the mag. Since then I have had the tractor out twice, one of the times being 3 hours and it got fully up to temp etc. It ran well then.

The only thing that I have changed recently was that I set the point gap to .015. (Fixed the slightly yellow spark) It was too wide before.

Does this sound like a bad condenser? Moisture again? Something else?

Thank you again

 

[Allan in NE]

Can't hear your tractor run, but what you describe sounds totally normal to me.

Those old one barrel Johns always run "lop-sided" like that under a no-load situation. Has something to do with the manner in which the fuel is delivered to the cylinders.

It's their "character".

Allan

 

[RAB]

How long a blue spark can you pull?
The points could be tried a tad closer - your points cam may be a little worn and you are opening before the magneto is at max current or your 15 thou is a tad generous. Doesn't sound like a condensor as they are usually good or bad, but you might check the 'apparent resistance rise' when cold and when hot and see if there is a big difference.

Personally it sounds to like a carburation problem and you are only apparently losing spark. Try choking just for an instant at these times and see if she starts firing again. It may be running just on the weak side. Also you could check to see if the spark is being lost using one of the indicator attachments available (although I can't recommend them for mag systems....) or a stobe light picked up from the plug lead HT.
There are other things like a loose safety gap electrode, moisture in the distributor cover or, indeed, in the mag if it has not been run a lot recently. I put my mags in the aring cupboard or in a cool oven to dry them if they have been in my shed for a while.
Hope this helps.
regards, RAB

 

[Anonymous-0]

Are you 100% sure that you don't have any moisture in your fuel. Small droplets of water getting sucked up through the carb will make for a missfire like condition. Then good fuel gets to the cylinder and the engine catches back to life. Might be a long shot, but worth a look.

 

[John T]

Dollar, That Wico X Mag has a bearing where the older C Mag has a bushing so they do a lil better in that regard. If theres excess shaft wobble running a lil wider points gap may provide temporary band aid relief. That loss of complete spark sounds like they may be some high voltage breakdown or arcing happening possibly from a cap or rotor problem. Id inspect the cap with a fine tooth comb to look for tiny cracks or carbon traces or unusual inner cap terminal or rotor tip problems like oil or moisture (use a hair dryer to heat up n dry her allll out) or carbon build up or shiny brass from rubbing. Make sure BOTH the caps lil springys, where it mates with the coil and the rotor are lining up n mating ok.
If it has the external push to kill button/switch make sure it nor its wiring isnt getting shorted.

If its NOT a cap or rotor problem and happens once all is warmed up, the coil could be breaking down internally or the condensor may be at fault. For no more than they cost Id replace the condensor and the points if they are burned or pitted or carboned up. Also insure the condensor is screwed down tight for a good ground and its wire to the points where the coil wire attaches are alllllll good n clean n tight.

If youre absolutely sure the points n condensor and cap n rotor are NOT at fault (try easy cheaper things first) and the cap is okay but she still seesm to totally shut down ignition wise, then Id suspect the coil is breaking down.

PS you might check the plug wires and use copper core if they need replaced.....

Let us know

John T

 

[old]

If its wired with a shut off switch check the switch and wire going to the switch it may be shorting out some place. Also the insulator going in the side of the mag will some times get bad and cracked and if that happens it can cause it to short out the mag and cause that type of problem
Hobby farm