Not knowing "the first thing about it personally" is the biggest perceived drawback to a magneto, and you're not alone. They can seem pretty mysterious, but you shouldn't let that scare you off. If they do fail, you either need to get a manual specific to working on the guts of them or send them out for repair. (There are, fortunately, some good mag shops around including magman, who hangs around this board, and Mainley Mags up in northern Maine. There are others, but I know those two and don't mind recommending either of them.) At the same time, most folks aren't set up to do the work on a battery distributor that has worn to where it needs work, either.
Myself, I like and prefer mags. If a tractor has one on it when I get it, I keep it, but battery ignitions are reliable, too, and I wouldn't go out of my way to convert a working battery ignition to magneto.
I don't like to say mag vs. distributor, because the mag has a distributor, as well. The difference is where the distributor gets its spark. For the battery ignition, the voltage from the spark comes from an external can that we all call a coil (it has two coils inside it, one inside the other, and isolated from each other) that gets its power from the battery. It's basically (and in terms that are too simplistic) a motor that's made so it can't turn. One coil sets up an electro-magnetic field that builds up into the other coil (a step-up transformer). Because it's all in a little can and nothing can turn, all the energy that would normally be used to turn a motor has to go somewhere. So it builds up while the points are closed, and releases as a strong enough current to make a spark when the points are opened. The current flows through the coil wire to the center post on the cap and is distributed to the spark plugs.
On a magneto, there's a spinning magnet in the middle, that generates an electro-magnetic field that is picked up by a coil that is built into the body of the mag. Just as in the battery ignition, this field build up while the points are closed and collapses when the points are opened to release the pent-up energy. At that point it flows to the "other part" of the magneto, which is nothing more than a distributor. It travels (on IH and others) through a wire (on many other types it's done inside) to a cap where the rotor distributes the energy to the plug wires.
There are die-hards with good arguments on both sides of the fence. My own observation is that battery and charging problems are far more common than magneto failures. If you have a battery and it fails, as long as you have a hand crank handy, and a magneto, being isolated from the rest of a tractor's electrical sytem, you can get started and keep running through cold weather, dead batteries, corroded connections, bad voltage regulators . . .
To my mind, there's a lot less to go wrong with a magneto than there is with a battery ignition as far as starting and running. BOth have points condeners, rotors and caps, but there are so many fewer components in a mgantoe system that are subject to problems in generating the spark. No battery, generator . . . and fewer connections and wires.
Bottom line (and this is worth the price you're paying for it). . . either system maintained well, will serve well.
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Today's Featured Article - Antique Tractor Solvents - by Curtis Von Fange. Solvents play an important role in keeping our tractor clean and running efficiently. There are many different types that can be used for external and internal cleaning of the various tractor parts. Being aware of the different types of solvents will make any cleaning job go easier because one can select the correct cleaning agent for the task at hand. Let’s take a quick look at what is available and readily used in the solvent larder of our shop environment. The most universal solvent in
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