Flywheel magnet keeps rusting?

What can I put on the magnet to stop it from rusting, and still allow the motor to start? I have to clean the magnet every time I attempt to start the mower and its getting to be a real pain in the neck.

Just paint it. Never ran across the problem because I don't worry about rust on the flywheel in my repair shop.

tim2 said:

What can I put on the magnet to stop it from rusting, and still allow the motor to start? I have to clean the magnet every time I attempt to start the mower and its getting to be a real pain in the neck.

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Can you post a picture of the rusty magnet?

My Lawnboy Flywheel Magnet was prone to rusting. I lightly sanded it, treated it with "Break-Free" oil and protectant and that was the end of the rusting.

I discovered Break-Free from a friend of mine whom was a maintenance mechanic at Disney World. He said they used it on all the rides to keep them lubricated and rust free in the Florida humidity. Break-Free has a very unique smell. After using it and then going on a few Disney World rides, I can absolutely verify that Disney uses Break-Free on their rides. You can smell it. It's also great for firearms and many other things around the house and shop. You can get it at Amazon or other online sources. My local Hardware Store also carries it.

I am sure there are some that will argue with this statement, but rust on the magnets will not stop production of spark unless the build up is so much that it stops the flywheel from spinning, thus impeding spark. In fact, that is one of the "trick questions" on the Briggs MST exam. If you have rust build up every time you go to use your mower, I would start by asking where the moisture is coming from? Secondly, I would check other some other things in the electrical system that may be being masked by working on the flywheel. Just some things that come to mind: is the spring clip on the high tension lead loose? maybe pulling it off and on wiggles the connection a bit to make it work, maybe pull the boot off to inspect, Is the grounding mechanism making good, constant contact? Bail brake? I'd be willing to bet that there is another issue.

Just my 2 cents.

d_sharier said:

I am sure there are some that will argue with this statement, but rust on the magnets will not stop production of spark unless the build up is so much that it stops the flywheel from spinning, thus impeding spark. In fact, that is one of the "trick questions" on the Briggs MST exam. If you have rust build up every time you go to use your mower, I would start by asking where the moisture is coming from? Secondly, I would check other some other things in the electrical system that may be being masked by working on the flywheel. Just some things that come to mind: is the spring clip on the high tension lead loose? maybe pulling it off and on wiggles the connection a bit to make it work, maybe pull the boot off to inspect, Is the grounding mechanism making good, constant contact? Bail brake? I'd be willing to bet that there is another issue.

Just my 2 cents.

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I always like the rust on flywheel question because for some for the guys that worked on the old point type engines, there was times you would have an engine with no fire, and you could remove the blower housing and clean the rust off the flywheel and then have spark. Some guys on here will argue that point to I will just leave it be. I think where the confusion sets in on the rust is it doesn't effect magnetism, but it does effect the air gap on the module. And on some engines where a thousand or two can mean he difference between starting or not, that is a big issue.

I always like the rust on flywheel question because for some for the guys that worked on the old point type engines, there was times you would have an engine with no fire, and you could remove the blower housing and clean the rust off the flywheel and then have spark. Some guys on here will argue that point to I will just leave it be. I think where the confusion sets in on the rust is it doesn't effect magnetism, but it does effect the air gap on the module. And on some engines where a thousand or two can mean he difference between starting or not, that is a big issue.

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That makes sense. Now I know Briggs tells us that in practical applications they don't produce an engine that is capable of having the air gap set "too wide" to produce spark. I will clarify this statement by saying that the mounts for the coil are in a fixed position. Given there location, a mounted coil can not be backed out far enough to "not produce spark". ( I clarified that statement for others who may read this, not you ILENGINE) I guess I don't recall much information speaking to an air gap that is to small. In my mind (yes a dangerous place LOL) I think I just assumed that if the flywheel could spin, then the lines of flux pass through the windings and subsequently generate spark. Can you share more on this? I consider it a start to a good day if I can learn something new while drinking my morning coffee.

Absolutely no reason to remove the rust from the magnets from a functioning point of view.
･ou can oil them or paint them i you find it annoying.
Most likely it will not be the magnets rusting as they are made from a weird sinter of cobalt niobium nickel none of which rust.
However the fly wheel will rust and some of this will be attracted to the magnets.
Where you do have to worry about rust is in the laminations and again a good oil will do the job nicely

d_sharier said:

That makes sense. Now I know Briggs tells us that in practical applications they don't produce an engine that is capable of having the air gap set "too wide" to produce spark. I will clarify this statement by saying that the mounts for the coil are in a fixed position. Given there location, a mounted coil can not be backed out far enough to "not produce spark". ( I clarified that statement for others who may read this, not you ILENGINE) I guess I don't recall much information speaking to an air gap that is to small. In my mind (yes a dangerous place LOL) I think I just assumed that if the flywheel could spin, then the lines of flux pass through the windings and subsequently generate spark. Can you share more on this? I consider it a start to a good day if I can learn something new while drinking my morning coffee.

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If I remember correctly the ones that I would see the remove rust to create spark engines were the older engines with points. Maybe the point systems were more touchy when it came to air gaps or what. Maybe it wasn't the rust on the magnet as much as the equal rust that was on the ignition module.

About three years ago I had a new push mower in the shop that wouldn't start with the electric starter, but would fire up and run on the first pull with the rope starter. Tried everything I could think of including replacing the carb, the spark plug, air filter, even tried swapping out the ignition module. On this engine the air gap was .008-.016 Found the only setting this engine would start at was .012 I had to vary the gap a thousandth at a time to find the sweet spot. At .011 or .013 would only start warm not cold. Only .012 would allow the engine to cold start using the electric start.

You work on this stuff long enough and you will find stuff that doesn't make sense, or will throw wisdom out the window. Examples like the briggs push mower engine that would only run with the spark plug wire disconnected and arcing about 1/4 inch to the spark plug connection. Or the briggs opposed twin, this is the one with one module, and two spark plug wires, would only create spark when one plug was disconnected.

I agree with posters on rust not affecting the ability magnetic field. However, lets review what rust is. It's the break down of steel/iron due moisture/water. This is why when the rust is cleaned away, the parts shows as pitted. The breakdown is composed of fine particles of decomposing steel/iron, which does affect the engines ability to start or make a spark. The accumulation of rust/fine particles can easily be enough, reducing the air gap to the point grounding out the coil, just like the ground wire would. It seems odd to me that many engine manufacturers have modified flywheels so the magnet portion is raised, in some cases quite a lot (Kohler CH Series). Just my two cents and 40+ years repairing!