Wico Magneto

On my 1945 hand start model A I think the mag is not firing the plug on the right (pulley) side. I have tested both plugs on the flywheel side and can see the spark jump when I turn the flywheel. However, when I check for a spark on the pulley side there is no spark. Plugs are Autolite 3116. Would anyone have smy suggestion as to what could be the problem? Thanks!
 
Could be a bad cap or a bad wire. Have you tries swapping the plug side to side and see if the problem follows the plug
 
Both plugs will fire on the flywheel side so I don't think it is the plugs. Plug wires from magneto to plugs are not that old. I wonder if something could be defective inside the mag
that is not sending any voltage to the right plug. How could I check that? I have had the tractor about 10 years and have never done anything to the mag. I may send it off for a complete rebuild.
 
Well, it is a process of elimination, and you have to go through it to find out what is bad.

You started the process by checking both plugs, so we know they are good. You also know one of your wires is good, so swap them around and see if you still have spark, if not, then you've got a bad wire. You possibly might have the wire come loose for the connectors on the ends. If that checks out, then you need to look at the cap and rotor. Look for corrosion or wear on the end of the rotor and on the contact lugs in the cap. You can clean the corrosion up, but wear means they will need to be replaced. Then check the points for pitting or corrosion, again cleaning the corrosion can be done, generally by putting part of a dollar bill between the points and working it back and forth, the linen the bill is made of is usually abrasive enough to clean the points. If they are pitted, they need to be replaced and if so, do the condenser at the same time.
 
A cracked cap can cause a problem like your having and a crack is very hard to find. One way to maybe find it but you will not like it is to spin it over and at the same time hold your hand on the cap. If you get zapped the cap is bad. I learned that the hard way back when I had a 1971 GMC pickup. Every time it got wet out it would not run right and my dad took it to a place to have the problem fixed. They could not find the problem but while there I told my dad to try to start it and I held my hand on the distributor cap. I got zapped and my dad told them it had a bad cap. They replaced the cap and fixed the problem but they tried to charge my dad for finding the problem and my dad told them they best pay me for doing there job and they shut up
 
To clarify, are you saying the cap on the magneto may be cracked. If so, why is there voltage to the plug on the flywheel side and not on the belt pulley side? Thanks!
 
If cracked the crack can be on the side you have not spark but the other side is not cracked so you have spark to that one. A crack can cause a short to ground due to moisture and cause a problem to in this case one side and not the other
 
Take an ohm meter and check the mag terminal from the outside terminal to the inside lug for resistance. No continuity will keep it from getting spark to the plug. Ron MN
 
Ray, first of all its the same set of points and condensor that fire so if ONLY one side produces a spark out the dist cap AND AFTER YOU SWAP SUBSTITUTE PLUGS N WIRES TO DETERMINE THEY ARE NOTTTTTTTTT THE PROBLEM

My suspect is its a dist cap or rotor problem

I have seen barely visible hairline cracks or carbon traces in the cap assembly cause this. Thoroughlly clean and inspect the cap. I have seen the caps INSIDE pickups (which the rotor passes by) have wear or carbon be sure to look at BOTH and/or the caps OUTSIDE terminals where the plug wires go in have problems.

Some later Wico X mags had two tip rotors and if so inspect BOTH. You need the right cap and right rotor

One other possibility is the shaft bushings are worn and the shaft wobbles which may cause a different gap on the two sides so only one side is firing

John T
 
You ask I wonder if something could be defective inside the mag
that is not sending any voltage to the right plug

Yep there could be something defective, HOWEVER there's ONLY ONE SET OF POINTS AND CONDENSOR that fires BOTH sides so Id suspect a hairline (maybe barely visible) crack or a carbon trace in the cap assembly or one of its INSIDE pick up terminals is bad like carbon or a crack or on the caps OUTSIDE where the plug wires fit there's a problem.

Ive seen the bushings go bad (moreso on C Mags than X Mags) and the shaft wobbles which could cause one side to misfire as the cam lobe isnt giving the right points gap.

After you swap substitute plugs and plug wires and find they are NOT the problem check the cap including its inner and outer terminals

The mags spring wind n trip impulse assembly needs to properly wind n trip each 180 when hand cranking

John T
 
you ask If so, why is there voltage to the plug on the flywheel side and not on the belt pulley side? Thanks!

A barely visible hairline crack in the cap orrrrrrr a carbon trace orrrrrrrrr a problem with the internal pickup inside the cap orrrrrrrrrrr the external tower where the plug wire fits could cause one side not to fire. The same set of points and condensor fires both sides.

John T
 
I usually rebuilt my own. It may be ONLY the cap or rotor that needs fixed but hey a professional total rebuild may be the best way to go.

John T
 
I checked it again this afternoon. There appears to be a hair line crack at the terminal where the plug wire from the belt pulley side (the side not working) connects to the magneto.
Pretty sure I will send the magneto for complete overhaul. Next step is to decide where to send it. Thanks
 

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