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Offline nadtiger

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fork stanchion movement in the fork assembly
« on: July 29, 2020, 10:13:40 PM »
I decided to give the head bearings a re-grease and noticed play in my fork stanchions.
I am able to hold the fork tube and rock the stanchions, back & forth.
is it normal ?
I just got my forks upgraded at traxxion with AK-20 cartridges.
I did not notice any knocking while riding though. 

Offline chuckxc

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Re: fork stanchion movement in the fork assembly
« Reply #1 on: July 29, 2020, 11:15:45 PM »
Are you doing this rocking while the front end is suspended with the suspension fully extended (off the ground) and unloaded? Can you see the movement or just feel it?
And are you sure you have now tightened the head bearings to spec?

Laterally unstable unless moving.

My third Triple - 1976 Laverda 3CL Jota
My 4cyl grunt - 2005 Honda CB1300F

Offline nadtiger

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Re: fork stanchion movement in the fork assembly
« Reply #2 on: July 29, 2020, 11:30:32 PM »
Are you doing this rocking while the front end is suspended with the suspension fully extended (off the ground) and unloaded?
Yes. Front wheel is up, off the ground and suspension is uploaded.

Can you see the movement or just feel it?
Cannot see the movement, felt it like it moves 1 mm all around.

And are you sure you have now tightened the head bearings to spec?
Yes, no play at the triple clamp as I tightened it, but there is some play in the stanchions.

I actually loosened it intentionally to see what a loose head bearing actually feels like.
I held the forks right above the stanchions and rocked it, felt the movement or clunk at the triple clamp.



Offline chuckxc

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Re: fork stanchion movement in the fork assembly
« Reply #3 on: July 29, 2020, 11:42:52 PM »
Ok, so its definitely not the headstock bearing.
With the forks fully extended like that,  there is the minimum amount of tube/stantion 'overlap' which could lead to that slight movement. Once the front end is back on the ground and loaded with to weight of the bike I suspect you won't feel it anymore. That would be to best test.
Laterally unstable unless moving.

My third Triple - 1976 Laverda 3CL Jota
My 4cyl grunt - 2005 Honda CB1300F

Offline nadtiger

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Re: fork stanchion movement in the fork assembly
« Reply #4 on: July 30, 2020, 03:04:23 AM »
That is correct. Once loaded I don't feel any play, even while riding.
Is the triumph head bearing setup tighter than other motorcycles in general ?

Offline chuckxc

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Re: fork stanchion movement in the fork assembly
« Reply #5 on: July 30, 2020, 08:09:59 AM »
Might be. My Honda CB1300, 245kg calls for only 25Nm on the headstock bearing nut.
Triumph Tiger 800 is 40Nm then again with 10 Nm.
Laterally unstable unless moving.

My third Triple - 1976 Laverda 3CL Jota
My 4cyl grunt - 2005 Honda CB1300F

Offline Newhorizons

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Re: fork stanchion movement in the fork assembly
« Reply #6 on: July 30, 2020, 01:59:42 PM »
My 2 bobs worth.

When I first got my Triumph I re greased the head stem bearings.

Having always struggled with getting the right torque and bearing preload I took another approach.

I once read about the weight technique. Which effectively means when everything is tight, there is a 'weight' range that the bars should move through.
So I have a small hand held spring scale. Fill a water bottle to Xoz , I think it was like 10oz and then note where the spring compresses to on the scale. That worked awesome on my Bandit with tapered bearings. I had flogged the previous lot out because it was a fraction loose and the bottom tapered bearing will flog into the cup at the front straight steering position. If that bearing cup is not overly flogged you can pop out the cup and move it around a bit but generally its better to replace it then.

So on the Tiger I put a cable tie on the grip and with the front wheel of the ground gently pull the bar with the spring weight tie until it moves. That is the approx weight to move the bars.

It can be a bit fiddly initially but it is a consistent way of measuring the 2 points, bearings and nut when all together at what you feel is the correct spec. You can normally tap the castellated nut at the top of the bearing a smidge to get to the happy place without having to remove the top tripple. So the final adjustments are not onerous.

Unfortunately during a big trip last year I started to get front end movement but quickly realised that the top nut had actually worked a little loose. And that nut does provide important preload. Make sure that the top fork clamp is lose on the legs during this bit and then re tighten after the HS is tight again.

Had to go to a auto place and buy a big impact socket but when nipped back up , was good as new. When I got home I put locktite on the nut, retested within range and should not experience that problem again.

So its easy to check every now and then by just pulling on the bar with the hand weigher.

If it clunks or click moves in your hands maybe your head bearings have damaged, the cup may have some wear (tapered bearings are considerably stronger as they have larger contact) but it may well be that your bearing torque is still out a fraction coz you have 2 critical points of pressure. You need to absolutely know they are right and then the biggest player in the field is eliminated.


Offline chuckxc

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Re: fork stanchion movement in the fork assembly
« Reply #7 on: July 31, 2020, 12:08:05 AM »
 :028:
And yet another 2 bobs worth in addition to the scale.....

I've also found the following technique  good for a quick routine  check while riding....

 Find a clear straight level road and when safe,  ride with hands off the bars. The bike should track dead straight by itself. The slightest wobble, indicates either the bearings are too loose or worse, a worn detent spot. 

You should be able to steer easily using knees in the tank and hands off. If the bike doesn't steer easily, or under-steers, the bearings could be too tight. If there is any worn detent in the bearing you will feel it as you try to steer.

Finally, speed up, throttle off, and hit the front brakes hard. You will instantly know if the bearings are too loose because you will feel a clunk.



« Last Edit: July 31, 2020, 12:11:44 AM by chuckxc »
Laterally unstable unless moving.

My third Triple - 1976 Laverda 3CL Jota
My 4cyl grunt - 2005 Honda CB1300F

Offline nadtiger

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Re: fork stanchion movement in the fork assembly
« Reply #8 on: July 31, 2020, 04:15:50 AM »
*Originally Posted by chuckxc [+]
:028:
And yet another 2 bobs worth in addition to the scale.....

I've also found the following technique  good for a quick routine  check while riding....

 Find a clear straight level road and when safe,  ride with hands off the bars. The bike should track dead straight by itself. The slightest wobble, indicates either the bearings are too loose or worse, a worn detent spot. 

You should be able to steer easily using knees in the tank and hands off. If the bike doesn't steer easily, or under-steers, the bearings could be too tight. If there is any worn detent in the bearing you will feel it as you try to steer.

Finally, speed up, throttle off, and hit the front brakes hard. You will instantly know if the bearings are too loose because you will feel a clunk.

Spot on.
Then it's definitely not my head bearings.
I got response from the shop (who worked on my forks) that the forks will have some play.
No issues while riding, so I rest my case. Thanks for all replies.

 


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