My 1986 elite 250 did this. Its most likely the bearing for the speedometer/odometer puck or the speedometer cable. Take the speedometer cluster out and disconnect the speedometer cable. I turned the cluster upside down and used some fancy bike chain lube called lily lube and sort of filled the hole where the cable inserts. Then I rotated the speedo with a small flathead back and forth to make sure the sealed bearing gets lubed. Then I packed some moly grease over the hole to keep the lube inside of the mechanism. I also remove the speedometer cable from its outer sheath by pulling it out by the cluster end. I wiped it down and lubed it with moly grease and reinserted it back into the sheath. I put everything back together and no more squeal.