spedometer won't sit still

[dalak79]

ok this is my third week or something like that, i notice and it is inconstant but my speedometer bounces. there does not seem to be any pattern and it doesn't seem to be bumpy terrain. it bounces even on flat surface with a steady throttle. some times it sticks and then drops? the fluctuation is about 4-7mph difference while going between 30 - 60mph. when i bought my first bike 450 nighthawk (a few years back) it had no speedometer but i used the tachometer and gear to determine speed until i got a speedometer. as you all know gz has no tachometer so i am a bit worried if i loose the speedometer.