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Aug 15, 2005
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Could someone explain to me what a magneto does or point me in the right direction. I'm trying to plan out the electrical system for my bike and am wondering what my options are; Magneto, Boyer, ect.

A magneto has a high voltage output so you don't need a coil for ignition. These are nearly all mechanical and have poor reliability compared to an electronic fired coil ignition.
It’s true that a magneto contains several mechanical components. For instance, it has a rotating armature running between permanent magnets and contact breakers. However, this mechanism is self-contained and generates its own electricity.

A coil system, on the other hand, does not generate its own electricity. Instead, it must be supplied with electricity from the battery and, in turn, the alternator. A coil system is worthless without a supply of current. In the end, a coil system requires nearly as many bits to run as a magneto, especially when you include the necessary battery and alternator.

Electronic ignition systems have eclipsed both coil and magneto systems. These ignitions have fewer moving parts but have increased electronic complexity. Moreover, they are inelegant to look at, in my opinion. In contrast, a magneto hanging off the side of a Norton provides a cool old school racing look.


Rasputin's Revenge MC
Member BGS

Magnetos wear rapidly at the armature brushes and bearings. That's why I said they are not reliable. If you can put up with the pain, go for the style.

Another disadvantage to the cool looking magneto is that it’s vulnerable to external damage. Retrofitting a magneto to an 850 Commando requires that you attach it to the timing cover, in place of the points plate. Once in place, the magneto sticks out quite a bit to the right side of the bike. It's easy to bang the magneto into something when, say, pushing the bike around in a crowded garage. And heaven forbid if accidentally dropped the bike on its right side, instant magneto death.

But I still love the way they look!


Thank you for the link: “How Things Work” I’ve saved it in my favorites!

Interestingly, the link repeated several times about how reliable magnetos are. And the link went on to say that magnetos were popular in small aircraft, owing to their “extreme” reliability. Also, I had forgotten about all the magnetos in lawnmowers edgers, weed eaters, etc. My mower never conked out from magneto failure.

However, Norton magnetos are probably not quite as reliable as the one in your lawn mower. There are no brushes to wear out but there are bearings, breaker points, and mechanical advance mechanisms that are prone to fail over time.

Thanks again for the link,

no problem.. that website is great to just sit around and read about how stuff works.. it rules!
after reading that and your post, i got to thinkin about other magnetos used with motorcycles, and if the norton magneto style was the only kind used on motorcycles? maybe we could get an ol cesna magneto onto a commando! haha

i like using the original mechanical parts on bikes, but im switching over to an electronic kind.. one reason is my gut tells me its more reliable, and two ive heard you can run more electronic accessories with it. i have a hid headlamp for my bike that i used from parts on ebay and i havent tried it yet on my current bike, but im sure it would put quite a strain on the system
Obviously, the boys over at "How Things Work" are not familiar with Mr. Joseph Lucas (the man who brought us "OFF-DIM-FLICKER") :wink:

Yup, mag's are generally pretty reliable. Pop's '36 Fordson (Bosch mag) has had spark forever!!!!!!


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