Generator output too high.

[Zephyr4]

I seem to have a later generator with the ribbed aluminium front plate and ventilated rear plate. I've cleaned up and re-adjusted the cut out switch. Finally, I now have current, but it's too high even with the 3rd brush adjusted all the way up. As soon as I'm up to a normal driving speed, the ammeter is reading 15 amps. I've put a voltmeter on the battery and it's reaching 8.3 volts with some rpm, which is higher than recommended I think.

Any suggestions as to my next step?