Magneto coil, CDI and magnet rotor

danlandberg

Member
Joined
Apr 25, 2009
Messages
569
Any one know about the magnet rotor?
Like; what Gauss is needed to create enough voltage/ current through the mag coil for the CDI to work efficiently?
According to the posts I have read, my mag and cdi ohm within specs. I realize the cdi might ohm ok but the capacitor might not be doing its job.
I can get the cheap inline spark tester (from Harbor Freight) to pulse dimly but can't get enough voltage to create a spark.
I have had two (2) magnet rotors go bad. They would not lift their weight off the bench with a screwdriver. One side of the rotor would and the other would not.
All grounds and connections are good. No kill switch hooked up. Has me baffled and confused.
I have two cdi boxes and two mag coils tried every combination with no luck. I have one magnet rotor I got from Gasbike.net , it will lift it's weight on both sides but you can feel the force is weaker on one side than the other.
I know magnets have the same pull force North & South to metal.
I made sure the air gap was equal all around. There is not that many miles on the engine, so I don't for-see bearings being bad enough to allow mag rotor to touch anything.
Any suggestions/ ideas ? Need input. THANKS
 


crassius

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Joined
Jul 23, 2012
Messages
4,575
most rotors I've seen vary a bit in pull between poles - lamination is to prevent hysteresis loss, but I'm guessing the chinese factories don't take care to be sure both ends are riveted equally tight

if you can spin it very fast and still not see the plug spark, I'd try another CDI first
 

Timbone

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Joined
Apr 20, 2014
Messages
1,104
Autozone sells a good spark tester for about $5. It will save you a lot of trouble.
 

Timbone

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Joined
Apr 20, 2014
Messages
1,104
It’s a very simple device, but excellent for our purposes. It’s a small, linear device that you can clamp to the cylinder head. Remove the plug and push the bike. You can literally see the spark. You can set for various test levels. If you have less that 25 kV then ignition is questionable.
 

machanic

Active Member
Joined
Jan 6, 2014
Messages
354
I usually get someone else to hold the wire:rolleyes: usually the guy who said it won't run because it has no spark, ends all doubt. As to the rotor being stronger on one side than other, make sure your screwdriver is not magnetized. If you have a rotor that lifts its own weight on a screwdriver that is more than strong enough.
 

danlandberg

Member
Joined
Apr 25, 2009
Messages
569
I don't like static electricity:eek:. I would let the lawn mower run out of gas before I pushed the metal kill tab against the spark plug . :eek::eek:
 
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