Mike T, what year/ model is your bike? I assume it's a Yamaha.
There are two nuts on the steering head. The steering stem locking nut is the one that holds the lower fork clamps and the steering stem into the head of the frame. This is what preloads the bearings. The steering stem nut is the one that hold the upper fork clamps to the stering stem.
Just to give you a comparison number, my manual states 59-73 ft lbs for a 1991-1995 RM-250. That is for the steering stem nut only, not the steering stem locking nut. When looking in my wonderfully indescript manual for the steering stem locking nut torque, the manual tells me to go to the torque chart. Of course nothing is listed in the chart for the locking nut.
I would suggest using a version of the automotive front wheel bearing method. Tighten the lock nut to the specified torque. Move the steering head from lock to lock about 5 times to seat the bearings. Losen the locking nut, then retighten until resistence is felt. Make sure the head moves freely.
I have used a "crows foot socket" for torqueing nuts in a tight spot. You could always remove the handle bars to get a regular socket on there.
Hope this helps, Steve.