HELP really need some speedo advise

[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