Nervous Speedometer

[ArchDruid]

Before I start taking things apart, I though I'd put it out there to see if someone could point me quickly in the right direction.
My speedo reading has always had a stable reading regardless of the speed. But now I've noticed the needle is getting a bit 'jumpy'. It gets worse the faster I go.
Starts getting nervous at about 50.   At 70 it bounces around between 65 & 75. And at about 120, its bouncing around between 100 & 140  ).
Anyone had a similar issue ?

[coffee]

Tell you what,I think I'd be bouncing about at 120 !!?   seriously,some of these speedos have a weird system inside and I don't think you're going to rectify it without foccing it up I'd try a breakers'.

[coffee]

Just thinking,it wouldn't be anything to do with the cable would it? maybe needing WD40 down it,that's if it's a cable I don't know anything about gen1's......don't know a fat lot about gen 2's either......don't know a lot about anything really....dooby doo doo doo daa 

[ArchDruid]

OK then, I think I'm just going to have to bite the bullet & get stuck in. Checking wiring connections is the easy bit. Maybe I'm lucky and its just dirty connections causing distortion at higher frequencies....
Really don't want to get down underneath to change the sensor if I don't have to. Its in an ungodly place at the back of the crankcase, close to the swingarm pivot ...  

[coffee]

Obviously not as straightforward as I thought ! don't envy you that one. Have you tried asking your local Yamaha dealer for any advise ?