Was riding around yesterday in 3rd gear,and tried to shift to 2nd. Shift lever went down, but did not pop back up,and transmission remained in 3rd. Shift lever moves up and down and will stay in either position(up or down). It does not pop back to the middle position as it should. Moving the lever does not change gears so I'm stuck in 3rd. Bike is a 2002 Rancher TRX350 manual shift. I'm a fairly competent backyard mechanic and would appreciate any info or advice. Thanks.