there's no spindle on your ap50, the big nut you are trying to undo screws onto the wheels driveshaft. if you can get someone to help you, get them to sit on your ped with the bike off the mainstand & pull in the brakes. now loosen the wheel nut turning in an anti-clockwise direction. to remind you when undoing nuts & bolts, turn left for loose & right for tight.
steo, June 2009