How to change the differential fluid on a GL1500SE

HI , ON THIS MODEL YOU HAVE A DRAIN PLUG AT THE BOTTOM, THIS WILL BE A 12 OR 14mm BOLT HEAD, REMOVE THIS BOLT AND THE OIL WILL DRAIN OUT. ON THE SIDE OF THE DIFF SLIGHTLY HIGHER UP YOU WILL SEE A 17mm SPANNER SIZED CAP THIS IS THE FILLER CAP, .SO UNDO THIS,IT MAY BE TIGHT AS IT HAS A RUBBER SEAL INSIDE IT, IF IT IS VERY TIGHT YOU MUST TAKE CARE NOT TO ROUND OF THE NUT AS IT ONLY ALUMINUM, A SIX SIDED SOCKET OR SPANER IS ,BEST.SOMETIMES A LITE TAP TO THE FACE OF THE NUT HELPS LOSEN IT. THE NUT ON THE TOP OF THE DIFF IS A BREATHER ONLY AND SHOULD NOT BE CONFUSED AS A FILLER, OR LEVEL WHEN YOU ARE SURE YOU HAVE ALL THE OLD OIL OUT INSPECT THE SEALING WASHER ON THE DRAIN PLUG BEFORE REPLACEING IT.
USEING THE CORRECT GRADE OF OIL FOR YOUR BIKE, GENTLY FILL THE DIFF, UNTILL IT BEGINS TO OVERFLOW,, ALOW SOME TIME FOR THE OIL TO SETTLE AND TOP UP WITH SOME MORE OIL UNTIL IT IS FULL AND NO LONGER DRIPS OUT OF THE FILLER, THIS IS THE CORECT LEVEL. REPLACE THE CAP TAKE CARE NOT TO OVERTIGHTEN AS CAP WILL SPLIT. WIPE AWAY ANY SPILLED OIL AND THE JOB IS FINISHED, HOPE THIS HELPS YOU, PAUL