Speedometer sensor test

[youngsonken]

I have a 1984 GL1200 Aspencade. I've had intermittent problems with my speedo not registering the speed. My Clymer workshop manual (P 220) describes the process of testing the sensor. I have done the test but the manual states (line 7). "The voltmeter needle should swing from 0-5 volts 8 times during one complete revolution". I get 10 volts 8 times per revolution not 5. Is this a printing error or a fault with the sensor? Advice would be very much appreciated.
Thank you

[oldishwinger]

the most common fault, with speedoes playing up is the gearbox on the left side of the front wheel, have you managed a check there?

[youngsonken]

Hi, yes, the gearbox is a new one (OEM) I bought only two years ago and looks and seems to be OK. The one it replaced had damage to the plastic insert.