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Discussion Starter #1
So I finally came round to getting a proper tool to adjust the steering head bearings with my 1/2" torque wrench. The main reason, besides convenience, was that I noticed that the manual prescribed a torque of 80Nm for the steering stem locknut on my K4 750. I figured that it was unlikely I would be getting even close to this value with a hook spanner, so perhaps that was explaining why I always had the feeling that the improvement I felt after tightening my steering bearings, seemed to vanish after a few days.

A drift or screwdriver and hammer would also work, but besides lacking in finesse, they don't allow any sort of method in the adjustment. That's because it's hard to tell how much you've tightened each component and since both the stem nut and the stem locknut contribute to the total preload on the bearings (and properly the stem head nut too), you're essentially left with trying at random, until you get a setting that's not too loose and not too tight.

A few thoughts on the procedure: It is my understanding, that the assembly is essentially that of three nuts in succession, with two washers in between. One is the washer between the stem nut and locknut and the other is the upper yoke, which seems to act as a washer between the stem head nut and the stem locknut (I'm using terminology from the service manual to avoid ambiguity here). What the point of this setup is, I don't know, but the manual specifically states that the stem head nut, should be fastened before the pinch bolts of the upper yoke, which should result in the yoke being tightened onto the locknut. The overall effect of this is that, as each nut is tightened each one contributes to the preload of the bearings.

This then means that the upper yoke should be removed, or, at least, both the stem head nut and the pinch bolts should be loosened before any attempt at adjusting the bearing is made. This is stated by the manual and it makes sense. What doesn't, is that the pinch bolts of the clip-ons should also be loosened according to the manual. One possible explanation, is that the clip-ons have locating tabs which might be resting against the top yoke, preventing it from being tightened properly against the stem locknut.

For me, the desired torque setting of the stem nut ended up being about 10Nm. This is very approximate, as it's the lowest setting on my torque wrench (which is of dubious precision anyway). Nevertheless about 10Nm seemed to be close to the threshold, where the bike started weaving at low speeds, wanting to fall into slow turns and requiring more steering effort. A smaller and better torque wrench might be useful here.

I have also puzzled over the purpose of the washer between stem nut and locknut. This has a tab, locating into a keyway machined into the stem, but no other tabs used to lock into the two nuts, as is usual. My understanding is that the locking effect is achieved through the increased tightening torque of the locknut and the purpose of the washer is to isolate the two nuts so that loosening the locknut in order to perform an adjustment, doesn't change the setting of the stem nut (as the washer is locked onto the stem and can't turn to transfer torque to the stem nut). Despite that, each time I've loosened the lock nut, the stem nut and dust seal turned a bit, or at least it looked that way. I can't explain how that could happen.

Not sure of the practical value of all this, as it doesn't really say anything more than the manual about the procedure. I've posted it here for whomever might be interested. Any thoughts and corrections are, of course, welcome.
 

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The washer is there so that tightening the lock nut does not further tighten the nut below it, and it is keyed to the shaft so that it does not rotate, because that would allow all 3 to rotate together and add more preload. The bottom nut is the only one that adjusts bearing preload. :dunno
 

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Discussion Starter #3
The washer is there so that tightening the lock nut does not further tighten the nut below it, and it is keyed to the shaft so that it does not rotate, because that would allow all 3 to rotate together and add more preload.
That's my understanding too.

The bottom nut is the only one that adjusts bearing preload. :dunno
It's hard to say much with certainty here, but generally, when you have two nuts jammed into each other, the total clamping force is increased by a certain amount, provided that you tighten the second nut more than the first (which is what's usually done). How much preload is added, depends on the slack between threads of the bolt (or in this case, the steering stem) and the nut, as well as on the elasticity of the bolt (steering stem).

In my experience it's not negligible. Without the tool, I didn't usually tighten the locknut enough to make a difference, but I've often noticed that a more or less properly adjusted steering bearing, ended up being too tight once the upper yoke was tightened down to the specified torque. This is essentially the same effect.
 

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The washer is there so that tightening the lock nut does not further tighten the nut below it, and it is keyed to the shaft so that it does not rotate, because that would allow all 3 to rotate together and add more preload.
That's my understanding too.

The bottom nut is the only one that adjusts bearing preload.
It's hard to say much with certainty here, but generally, when you have two nuts jammed into each other, the total clamping force is increased by a certain amount, provided that you tighten the second nut more than the first (which is what's usually done). How much preload is added, depends on the slack between threads of the bolt (or in this case, the steering stem) and the nut, as well as on the elasticity of the bolt (steering stem).

In my experience it's not negligible. Without the tool, I didn't usually tighten the locknut enough to make a difference, but I've often noticed that a more or less properly adjusted steering bearing, ended up being too tight once the upper yoke was tightened down to the specified torque. This is essentially the same effect.
I confirm entirely. And if you make the conversion (from sphere to roller), the window of the right adjustment is much more smaller than sphere...( in 10-15 degreees you passes from too loose to too tight). it s very very difficult reach the right adjustment after evrything has been correctly tightnened
 

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Quick question lads...how tight should the lock nut above the washer be? I'm trying to loosen it with a screwdriver and hammer and it ain't shifting! Would a be better with a C Spanner and if so what size? Is is a reverse thread?

Thanks
M
 

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Discussion Starter #6
The manual specifies 80 Nm, so it's meant to be tight, but who knows how much it was actually tightened. The best tool for the job, since a C spanner is tough to get in there, would be Suzuki's special tool, or, since it probably costs an arm and a leg, one of the copies of it you can find on eBay and the like. I'm pretty sure it's not a reverse thread.
 
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