The Bullet: Mysteries & Myths -
Don't just love but get to know your bullet more

- by B. R. Gurunandan

Setting the Rotor-Stator Gap

Whenever the Stator and/ or Rotor have been removed or disturbed, it is necessary on reassembly to verify they they are coaxial and that the gap is uniform. In practice, this is all too often neglected, leading to scoring of the surfaces, and sometimes failure by overheating.

Assuming the rotor and stator are in place, push a film-strip or plastic-sheet
between each coil and the rotor. You should be able to do this with all the
six coils. If it fails in all cases, you need a thinner strip, but if it fails with one or two coils, slacken the stator holding nuts a bit and tap the stator gently on the opposite coil outer till the strip is just free. Immediately check that the gap under the opposite coils has not closed up. As shown in the picture, the easiest way to do this is with six strips in place, making sure all are free. When they are, tighten the stator-holding nuts firmly and then remove the strips.

Now turn the rotor to another position and check the gap. Repeat yet again. This is to rule out run-out.

If there is run-out, it is most likely due to un-clean surfaces between the shaft and rotor. Remove the rotor and clean both surfaces very thoroughly, not forgetting the keyway and keyslot.

It is a good habit to verify this every time the primary cover is off for any work on clutch or chain. Loosening of the rotor or stator fastening by vibrations may thus be caught before it's destructive effects are observed.

By B. R. Gurunandan

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