On my Xciting 500 2007, you get to the spark plug by opening the middle panel (one screw, kind of between your ankles when you're sitting on the bike). Look in there with a flashlight and mirror, you might be able to see the top of the plug toward the rear, recessed in the cylinder head. Anyway, you pull the spark plug wire loose, then use the long spark plug socket, which on my scooter is attached with the tool kit on the underside of the seat. Not easy to see or do first time, but once you know where it is, it's pretty easy to do by feel.