tachometer fluctuation kz550

my tach fluctuates about 100-250 rpm when idling. what would be a common issue to cause this?

If your engine is idling smooth and you feel it is the gauge that not working right, you could try pulling the inner cable out of the tachometer housing and lubricating it. Also, try re-routing the cable if the lube does not help. My tachometer and speedometer jump around quite a bit on my '81 KZ550D1, but not at idle.

Robert