6th Gear

Folks, please be gentle with me on this one.
My '1985 GPZ 550 has 6 gears or so it says on the clutch cover but I cannot engage 6th...any solutions, reasons or why ?
Many thanks
Hog.

Need more info, does it go thru the other gears ok, is it running or off, did this problem just start or always been there, ect?

Baldy 110.
The bike is a new to me bike so I was not sure if there were issues before.
However to get it out in the open it was stupidity and use error.
The bike does have 6 gears and I have now mastered the art of the 6th gear.:blush: :blush: :blush:
Many thanks for the help.
Hog.