HELP really need some speedo advise

[Disorderlypunk]

HELP
my speedo packed up the other day so i stripped the front down and found the rotor sensor damaged
---no diagnosis readings given on rev counter----(did once while riding but only once)
new one fitted and put together CORRECTLY no snapped lugs etc
still no speedo, getting no pulse signal to the spedometer (white wire) just sits at 3.8V
readings on the loom side of the speedo plug
blue and yellow - 12V /  white 4.61V / black and blue 0V and earths
if anyone could test that they have 4.61V on there white wire would be helpfull as that is the only one i dont think should have any voltage


all advise will be taken its driving me and my father nuts (we hate modern electronics)

[Disorderlypunk]

damnit looks like im going to have to buy a speedo sensor and hope its that
thank god for ebay cause £100 is just ridiculous

[Disorderlypunk]

interesting development i measured the white wire today all plugged in (use a pin) and the speedo was jumping all over the place
(no rotator in the sensor)
measured the voltage and it was jumping all over the place at times then doing nothing at others
same thing happened when i put the rotator in and spun it
ordered a new sensor from fleabay for £30

[BBROWN1664]

Check for damaged wires on the cable that goes from the sensor up to the speedo. Common problem for them to rub and wear through. Completely fixable though.

[Disorderlypunk]

i checked them yesterday hoping that was the problem but everything was fine
the original rotor was cracked and i took the bike through a flood last week so i have a feeling some water may have got into the sensor and fried something
when the new one arrives i might disect it to see whats actually inside one of those
-first time i have worked on a dodgy electronic speedo i dont normally bother with speedos at all
wouldnt bother at all if it didnt screw with the ignition timing