no,
but depending on what SX you are looking at there might already be a primary 5th & 6th gear already in the trans, bust the cases and install a couple of gears and remove the shift mechanism lock pin and WOLLA 6sp.
2003 Husaberg FS-SMR 550 style
WEIMERANERS.......FTMFW
always demand perfection, in everything- orders, women, beer, wine, sex, christmas, the performance of your motorcycle, your waitress when she serves your bacon and eggs sunny side down- and you'll always be set-up for disappointment.