How to correctly adjust steering head bearings

[2WheelsUp]

I found my steering head had excessive play in my recently restored Le Mans. Understand that I never adjusted, let alone installed, my own bearings in my life until now. When I initially installed the bearings and set the tightness, I did it while only the top/bottom yokes on and forget about it for the next 400 miles until around 50 miles ago when I detected some play when going slowly over railroad tracks. Clearly I should have checked them again once the weight of entire front end was on the bike, but that said the other day I tightened the nut to remove the play to the point where there is free unrestricted movement lock to lock while the front wheel is off the ground. I can position the forks anywhere in around 75% of the arc without having them flop to the side. I read the service manual... something about tight enough to hold it's position but bumping it causes the forks to fall to the stop... not very precise instructions but I'm sort of there... more to the left side than the right side, seems like the brake lines are affecting the flop to the right side. I wouldn't be concerned except for the caution note in the service manual about setting them too tight. So what is the practical correct procedure to set the tightness of the steering head bearings?

FWIW, when I rode it afterwards (with the damper engaged), I could tell immediately things were tighter, seemed smoother and rolled better over imperfections in the road. Before the bike sort of fell into curves to the point where it felt like it would just fall over if I didn't hold it up whereas now it's more on a rail and holds it position in a curve until I power out of it or make an adjustment. It now seems to steer more like my modern Ducati 939 Supersport. Overall I like it better but I'm a bit concerned I may have it too tight... more so when I'm going slow (under 15 mph) through a rotary or maneuvering through a parking lot, I have to "steer" it more... wants to go straight. I haven't detected any weaving or issues at higher speeds (15-80 mph). What are the symptoms I should be looking for when the bearings are too tight and what's the worse that can likely happen?

[Two Checks]

When they are too tight you have to constantly make steering corrections. When you make a correction it tends to stay in that direction until the next correction. Then repeat.
When tightening the bearings loosen the bottom fork clamp only. Leave top clamps tight with forks even with the clamp. You don't want the forks to sit higher in the clamps, it affects steering angle. It sounds like you have them pretty well adjusted.
I have also put the bike on the c-atand, put the bars at full lock then raise the front wheel and drop it while holding the grip with two fingers. If the bars bounce side to side they are loose. You will also feel the stem bounce in the bearings.
Good opportunity to clean and grease the bearings. Guido and Luigi are known to not grease them.

[moto-uno]

 It sounds like your pretty close to correct . The caution concerning over tight
neck bearing adjustment, is that it tends to lead to high speed weaves , very disconcerting .   Peter

[berniebee]

Not surprising that some play developed after installing new bearings.
Yes, too tight is worse than a little too loose - for riding, anyway. Tight sticky steering can lead to weird balance and steering problems. And your bearings won't last long. But a bearing with play will pound notches into the race pretty quickly.


My adjustment method is simple and (I think) universal: Disconnect everything that you can that will affect the feel of the fork steering rotation- speedo and tach cables, brake line, etc. Loosen the lower triple tree clamp bolts. Turn the steering head adjustment nut until there is no play, but the forks are still easy to turn. What is "easy to turn"? Ideally as easy (or almost) to turn as if the bearings are too loose. Experiment and you'll see. The important point here is that you should feel no binding at any point in the rotation AND no play. Once you are satisfied, tighten the locknut and check again. Often after the locknut is tightened, the bearings will be too tight. You might have to loosen the adjustment nut 1/8 turn and retighten the locknut. It can take several attempts, that's normal.

[PeteS]

I have been using essentially the same technique. Tighten so its snug then back off to the point where just tapping the bar right or left causes it to flop over. As for the damper, mine (LM850) has been removed for decades. Never needed it even for track days. Friction dampers are useless anyways. They work the opposite of ideal with highest friction with no movement and less the faster the turn. Hydraulic dampers work just the opposite.

Pete

[guzziart]

FWIW...

For checking head bearing preload I've used a method described in the Honda Goldwing maintenance manual.  Basically, to check preload after you have adjusted the head bearing or replaced them or have confirmed that they are in serviceable condition, using a fish scale, attach the scale to one of the fork legs underneath the lower clamp and pull it through lock to lock.  An acceptable amount of force to pull the fork lock to lock is 3-5Lbs.  I've used this method on my other bikes with good results. 
To attach the fish scale, I utilize a reusable ty-rap and place it loosely around the fork then hook the fish scale through the ty-rap.
I don't know how much it matters what the head bearing stem nut is torqued to (my experience is usually 20-25lbs.ft) in preloading the head bearing as long as after the stem nut & lock nut are tightened down the result is 3-5lbs. of pull is required to go lock to lock.
And, the front wheel is off the bike when I do the head bearing preload fish scale check.

[2WheelsUp]

Thanks for all the advice. I'm going to take another stab at adjusting them since I suspect it's a bit too tight.  @guzziart, sounds like an objective way of setting them.  I don't have a fish scale, maybe in future, but I'll just use other techniques mentioned.

[guzziart]

Thanks for all the advice. I'm going to take another stab at adjusting them since I suspect it's a bit too tight.  @guzziart, sounds like an objective way of setting them.  I don't have a fish scale, maybe in future, but I'll just use other techniques mentioned.

Fish scale weight devices are sold at Walmart (Ozark Trail brand), Dicks Sporting Goods, Bait shops or any lace selling fishing stuff.  I have a couple, one was from Walmart for under $10.  Besides using to check bearing preload, I use one for weighing my 20lb propane tank so I know when I'm close to needing to getting it refilled.