Speedo flutter
The odometer would be an LCD screen instead of the numbered wheels that spin to indicate distance traveled if electronic.
You state "Always had the issue when >100 mph".
Since you state "always" does that mean you have owned the bike since 1996 and you never had the bike into a dealer for warranty work??
If it is an electronic speedometer:
If the motorcycle is operating correctly then i would take a look at voltage at battery posts with a digital voltage meter.
Basically looking for an over voltage or loss of voltage situation as you increase RPM. Review the charging system.
A voltage spike or unsteady voltage could cause an electronic speedometer to function incorrectly.
If somebody re-routed speed sensor wire really close to a spark plug wire then signal interference could be possible.
I would also remove the speed sensor and review for metal filings too.
Their is a possibility that speedometer itself could be defective but a test would rule that out.
If it is a cable speedometer then the speedometer drive at front wheel, cable or speedometer requires review.











