Motorcycle Repair: speedometer, speedometer needle, kawasaki zx

Question
I have a 99 Kawasaki ZX 6R. At about 80-90mph the speedometer needle twitches about 10mph each way. I've replaced the instrument cluster with a factory new one and replaced the signal sender and the twitching remains. It's not a cable speedo. The lip of the front wheel has a slight bend in it from a poor job with a tire iron by a shop. Any suggestions as to what is causing this problem?

Answer
Mark,
did you replace the sensor near the front sprocket?
Is the sensor grounded well and is it
clean where the sensor gets it's reading?
Unfortunately it is possible to get
faulty new parts. If your old speedo and sensor
do the same it is likely some poor connection
or possibly vibration or component wear
at that speed. The sprocket where the sensor
is checking the speed could be slighty
off due to transmission bearing wear.
Have you tried a different battery or
cleaning the fuse connectors well?
If it isn't the components, it has
to be the wiring, connectors or mechanical wear.
The yellow wire from the speed sensor
goes up to the speedo, check that. Also
there is a big junction box under the seat,
could be a poor connection in there.
Could be an ignition ignitor problem or ECU since
I am sure it has some connection. Sometimes
gauges will flicker because of computer faults.
If I think of anything else I'll post a follow-up.