Thursday, October 13, 2016

Quick and Easy Magneto Check

This is a simple check that can save you some time, aggravation, and maybe even some money.

You have a used mag, or you are swap meet shopping for one.  Is it in working condition?  How do you know if the mag is not in a bike and/or the bike doesn't run?  Or is that magneto equipped  bike you have had for decades becoming harder and harder to start, and you suspect it may be more than just symptoms of an old leg?

Easy.  And best of all, a minimal investment in test equipment.

That's right, two 3/8" bolts and a rubber band.  Even with the mag out of the bike and spinning it by hand, a magneto in good condition should be capable of jumping the gap between the two bolts.  If you take that tiny little drive gear and give it a vigorous twist, it should produce a spark.  Obviously then, if the mag is still in the bike, it should do the same at "kicking" speed.

I learned this little trick over 25 years ago from the local magneto guru, Neil at Electro Mag Specialties.  Well, Neil is no longer with us, but before he passed on he served as a mentor to a gentleman I recently had the pleasure of dealing with, that being Rudy at When I mentioned the trick that Neil taught me so many years ago, he confirmed that a magneto in good condition should be able to jump a 3/4 inch gap.

One caveat to mention, however; if your magneto is of recent vintage with "rare earth magnets" or has been updated with them, this trick will not work.  I suspect it is because these new "hi-zoot" magnets produce just enough more drag to prevent you from getting enough speed into your twist.

Another point I might add. It has been my experience that if your magneto has weak or no spark, and its not the points, then its usually the case that the magnet needs a re-charge.  This is especially suspect if the mag worked fine and rather than failing while in use, it was left unused for a long period of time or gradually became weaker. Here is a situation where a service such as Rudy provides can really shine.  His charge to service a magneto is only $45, plus a mere $15 additional to recharge the magnet.  That means that if the rest of your magneto is good, then for only $60 it can be back in tip top shape.  And when it comes to starting a magneto equipped bike, that can save a young guy from having an overly muscular right leg (it makes you look weird to have one leg twice as big around as the other), and for we who are older it could prevent a heart attack. 

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