Speedo needle bounces when...

[Duck-Stew]

Charlie98 made a good point.  As long as you have 12 volts the sensor will be happy, but your dash, maybe not.  Weak batteries play havoc on electronics.

I forget which, but some of the sensors run 5V power, so don’t freak out if you see 5V on the supply side.

[stopintime]

Got a new'ish battery. Made no difference to the needle - it was already steady.

The old battery sounded wounded after one or two 'churns' on the starter. The new sounds fresh, churns at 11.3/11.4 and charges up to 13.8 after a ride.

Thanks guys 

[booger]

I had an issue like this with my former S2R. It happened around 55mph, the needle would behave like it was caught on something for a half second then snap to correct speed. I always thought it was something in the cluster, like one of those tiny stepper motors the needle is mounted to was going out. Never bothered me so I didn't fix it. Nice to know that I could have fixed it though, perhaps maybe, with a new sensor.

[stopintime]

The fresh battery was load tested - 100 amp they said. Another guy said this is twice what you'd normally load a car battery with. Might have killed it....   Anyway, it died properly dead during my Alps & Italy tour in July. The days before I had a few hick ups from the engine and a couple of "batt" dash warnings. New battery from an angel. No more trouble since.