Front wheel axle doesn't have a castle nut.
The front axle is screwed together before you mount it to the forks. There is one spacer on the left, the "spacer" on the right is part of the speedometer drive.
When you tighten the axle bolt, the axle should be tight against the spacers, no play.
A picture might clear up what problem you are having. Take pictures of both sides.
Point out any suspicious points, if you have any suspicions...