2004-2005 Honda TRX450R Factory Sevice Manual, Page 203Get this manual
CRANKCASETRANSMISSIONCRANKSHAFTBALANCER In stall he su nk key into he key groove in he balancer shaft
Install the balancer driven gear onto the balancer shaft by aligning th key roove with the key
Install th balancer driv gear nto th cra nkshaft by ali gni ng th ide groove ith he lat tooth (p unc mark)M esh the balancer drive and driven gears hile aligning the punch marks as shown