the bike has 40,000 m on it will shift up through the gears but will not go down, the shifter feels a little soft. got any ideas? im not a newby been riding and wrenching since i was 20 (51 now)

1984 kawasaki ltd 700 current project
1981 kawasaki ltd 440
1996 honda 600f3 sons bike
2000 yamaha yz125 next project