Steering head bearing adjustment is a topic of nearly perennial conversation. Not quite so abundant as battery charging, but close 8-)
One possible explanation is that factory specifications, at least for Honda's VFR and Suzuki's SV650, impose a relatively large preload on the bearings sufficient to destroy them in a few thousand miles of riding. Combine this with an adjustment retainer designed by a descendant of Rube Goldberg and we're all set for endless steering troubles.
First, here's my interpretation of the factory's intention; the procedure is drawn from a '98 vfr800 service manual. The manual gives no indication of "why", I'm speculating freely on the author's motivation.
Step one is to assemble the bearings, seat the races and finalize the race seating by torquing the bottom nut to perhaps fifteen ft-lbs. Moving the steering lock-to-lock a few times ensures that the outer races are seated in the frame and the inner races are seated on the stem. Step two is to back off the bottom nut and re-tighten it until the turning friction of the forks is half to one pound applied at the fork tube. On a VFR that works out to very nearly 1-2 ft-lbs of bearing friction and is completely different from the torque on the adjuster nut, which will probably be greater.
Now the procedure gets subtle: The instructions are to run down the second nut, close but not touching the first, and drop on a lock washer which engages the first nut. Then a third nut is run down to trap the second nut, lock washer and first nut.
All well and good, provided one tightens the third nut without rotating the washer and thereby spoiling the first nut's setting. That's not easy to accomplish.
The idea is to set the preload with the first nut and use two nuts plus a lockwasher to hold the setting. In principle it's precise though somewhat difficult to do. The major blunder is setting the bearing preload too tight, ensuring that the races will get "brinnelled", with the balls chewing divots into them and probably flat-spotting the balls in the bargain.
On my vfr the steering got notchy, when I took it apart I found the lockwasher twisted into oblivion. Apparently the overloaded bearing twisted the top race, which turned the bottom nut hard enough to bend the lockwasher out of engagement.
Being old enough to have adjusted front wheel bearings on VW Beetles (the air-cooled kind, not the new ones!) I realized that the preload adjustment on the VFR was huge , larger than the preload used on a VW bug's front wheels, with much larger bearings.
This led me to try a modified procedure, thus:
Assemble and seat the bearings as usual, then back the bottom nut off till it turns with fingers. Tighten it, with fingers only, till the play seems gone.
Twist, turn, pry and otherwise attempt to detect any play in the steering stem. Axial, radial, whatever. If there is play, and the nut is finger tight, some sort of assembly error has occurred. Take it apart and start over. Probably a race is not seated properly. If there is bind, likewise something is wrong....take it apart......
Finger tight, no play, no bind? Good! Now run down the second nut and hold the first securely. Tighten the second nut to maybe 20 ft-lbs, perhaps a little more, without letting the bottom nut turn.
This is what sets the preload. Finger-tight on the first nut takes out the freeplay, 20 ft-lbs on the second stretches the steering stem by the axial clearance between the threads of the stem and first nut. Not a lot of stretch; a few thousandths of an inch. On that scale the stem is fairly rubbery.
20 ft-lbs on the second nut does something else, it locks things tight enough so the third nut can be run down and torqued to factory spec without too much risk of twisting the first nut. Still, one has to be careful; if the bottom nut moves after the initial finger-tightening the whole process must be repeated.
At this point the top triple clamp can go back on, with the top nut tightened to whatever the manual says. The bottom nut is no longer applying force to the bearing, but instead resisting forces applied by the top nut. The second and third nuts nuts are essentially spacers.
Following this procedure will result in substantially less steering friction than the factory manual. In my experience (replaced vfr head bearings at ~24k miles, now at > 67k miles) the preload is entirely sufficient. The bike steers perfectly, no bind, no play, no headshake. If I were a better rider I could set the VistaCruise and proceed with no hands. All disclaimers apply, YMMV and all that.