Husqvarna TC 450 Workshop Manual page 221

FRONT SUSPENSION
Remove the cartridge unit from the outer tube.
Do not remove the nut in the lower part of the cartridge unit.
Remove the bottom valve unit from the cartridge unit
Lock the outer octagonal area of the cartridge assembly into place using a
suitable tool.
Use a similar tool in the internal octagonal part of the bottom valve unit.
Using a spanner, loosen the bottom valve unit.
Check that the O-rings on the bottom valve unit are not damaged.
Replace if necessary.
I.29
Part. N. 8000 H1344 (10-2009)