rev-counter jumping 2006 vfr 800

Hi folks ! im riding 06 vfr800 interceptor for a last year. and i have issues with rev counter, needle is jumping up and down, has anyone came across this issue?
yellow/green wire is 9.3v. new battery, alternator and R/R.
Thanks

 

Check the plastic piece in the coupling between sensor and sprocket



Ref.44808-MR7-013

 

this is speed sensor but for me is jumping rev-counter (tacho) its needle jumping up and down but engine working nice