Where to Start When the 90/6 Won't Start

jimmylee said:

He learned from others on the K-bike forum that the problem was the starter brushes being either dirty or need replacing. He took apart his starter, cleaned the brushes (which didn't need replacing) and commutator and voila! Took about an hour. Everything is again working perfectly! Does that seem logical that the starter brushes needing cleaning would cause the lights to flicker?

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PGlaves said:

Yes, beccause the designers wanted the headlight and other loads to go off when the starter was running. So they installed what is in essence a headlight relay called the load shed relay. They grounded the relay coil to the starter brush.

Thus, +12v applied to the relay coil, grounded at the starter brush energizes the relay and the lights are on. But when the starter button is depressed +12v is applied to the starter. Back at that relay coil it sees +12v on both sides, lacks a ground, and disengages the relay. The lights go off as planned. Release the starter button, the relay coil regains ground and the lights come on.

If the brush is worn or dirty and making poor contact, the load shed relay loses its good ground even with the starter not energized and the lights might flicker or just fail to come on at all.

I wrote about this in this month's Benchwrenching in the Owners News.

It is a simple rather elegant solution actually.

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