The Ten Commandments of the
CBX Alternator Drive Clutch

  1. Contrary to popular belief, the CBX alternator rotor isn't supposed to slip intermittently. It should hardly slip at all, and no more than one-fourth revolution when it does slip -- just enough to take the peak off the torque shock (curve) that the primary shaft and parts feel.
  2. The parts being protected here arenít the alternator parts at all, but the primary shaft and primary chain. The alternator rotor isnít in danger. The very same design is used on other bikes whose engines rev equally aggressively, and their rotors are on the ends of their crankshafts.
  3. The clutch drive disc is defective on all CBXs. By a mistake in design, the drive disc is manufactured cup-shaped, with the result that only a fraction of the design surface area contact is realized between the two discs.
  4. An as-manufactured CBX engine-side (drive) alternator clutch disc. A straightedge is being held onto its surface. Image courtesy of Nils Menten.

  5. Consequently, the clutch slips far more often than it is supposed to, and several revolutions each time it slips instead of just a quarter turn or so. The result is overheating of the discs, and subsequent work hardening, galling, and hugely accelerated disc wear.
  6. The final result is that the clutch disc pack rapidly becomes thinner, reducing spring tension and promoting even more slip.
  7. Sanding the discs (both of them) does three important things. A) It flattens the discs, especially the defectively made drive disc. B) It removes the disc galling, especially around the oil groove area. C) It removes disc glazing, that is, the work-hardened skin that makes the clutch slip even more.
  8. Adding another steel washer brings the clutch packís spring tension back up to design specs, by making up for the worn and sanded discs. Buy the shim here.
  9. The washer also restores normal spring tension by compensating for a "sacked" spring, and in any case puts the tension back in the normal range. This benefit is minor however compared with the one above. Don't fixate on the spring, focus on the preload.
  10. Resist the temptation to make this shim the whole fix, it is far from that. If the clutch is not serviced as described here, the extra washer will do little more than slightly extend the inevitable need for that service.
  11. Remember, it's not a matter of "if," but "when." The discs are made bad. Even a Cycle World article (January 1979) mentioned the bad alternator clutch in its early test article, though they mistook it as a normal characteristic (!). All the drive clutches are bad, and they are all bad out of the crate.

The procedure for reconditioning the clutch discs is found in my CBX Charging booklet. It goes into all the steps of bringing your charging system up to snuff. The booklet can be ordered by clicking on the booklet image.

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© 1996-2016 Mike Nixon