I have a fluctuation speedo...started about the same time my ABS unit was getting ready to go. I checked the sending unit, I checked the wiring to and from and all around (did you know how much wiring there is on an S? There's ALOT.)..I checked the connections on the back of the instrument assy, cleaned ALL the contacts, put dielectric grease on them and nothing happened. As time went on the ABS unit started to fault out all the time and finally died altogether...twice actually. At the final days of the ABS unit the speedo started to act exactly like the tach. Very strange.

The bike is getting a brand new ABS unit now after I tried a used one that did not work properly, so I'll have to let you know what the speedo is doing when I get the bike back.

I'm not saying the 2 are related but there has been some weird electric stuff going on as that ABS unit fizzled. Brake light staying on all the time was another trick.

Good luck searching it out and let us all know what you find out as time goes on and I'll do the same.

I have a similar problem. my speedo will act like the tach every so often. I notice this right after installation of Laser exhaust and chip. It still register speed normally, but when I blip the throttle at rest, the speedo will move up and down with the tach. Wier!!:confused:

See Moki, it's funny you should mention that.... I was gonna say that I was wondering if the Motronic could be playing into this somehow. I almost am ready to pull the motronic and replace it before I would do the instr assy if the problem persists after the ABS unit goes in.

Check the connection at the end of the sending unit ( where it connects w/ the wiring harness ) - this has been a problem for many of us...

jeff

My speedo went bad and acted like you described. The problem is in the rear end drive unit. A metal part that is attached to a drive gear has come loose from the gear it is fixed to. This part is what creats the magnetic field for the magnetic pick up unit. The result is a flickering speedo that reads about 1/3 the actual speed. the Odometer is affected at the same ratio. I am told the repair will be pricey.