Crank magnet identification 12 vs 18 pole

[boontonmike]

What are the ways to identify the differences between the 18 and 12 pole stator crank magnets. I have a 78 550 bottom end that I just ordered an OEM 12 pole stator for to find out there was an 18pole stator on the bike. I'm curious to see if the magnet was changed to make this work.

[tom203]

What are the ways to identify the differences between the 18 and 12 pole stator crank magnets. I have a 78 550 bottom end that I just ordered an OEM 12 pole stator for to find out there was an 18pole stator on the bike. I'm curious to see if the magnet was changed to make this work.

While the stators are considered 18 or 12 poles - the matching rotors would have 6 pairs of N /S magnets for the 18 pole stator or 4 pairs of N/S magnets for the 12 pole stator- this is due to the 3 phase windings.
To find out what you got, get a small round magnet (like off your refrigerator), one side is N and the other is S- the N side will be attracted to the S pole in your rotor, while the N side will be repulsed by the N pole in rotor. Move your little magnet around inside the rotor and you will quickly figure out how many magnet pairs you got.
Some folks changed out the 12 pole for the 18 pole rotor- it likely gives higher output at same RPM.

[Steve]

You should be able to look on the inside of the magnet surface and see lines between the magnets. I think the 18-pole systems have three separate magnets, so you will see three joints around the circumference. The 12-pole systems will have two magnets, therefore only two joints.

You can also take a small screwdriver around the inside of the magnet and count how many times it is attracted to it as you go around the circle. The driver will be pulled to one area, then, as you pull it around the circle, will jump to the next area, and so forth, all the way around. WARNING, you will have a VERY magnetized screwdriver when you are done.

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[SqDancerLynn1]

They are NOT interchangeable