Yamaha WR450F(W) Owner's Service Manual page 780

T U N
SETTING
CAUTION:
When using a rear cushion other than cur-
rently installed, use the one whose overall
length a does not exceed the standard as
it may result in faulty performance. Never
use one whose overall length is greater
than standard.
Length a of standard shock:
488.5 mm (19.23 in)
7 - 17