Head bearing top yolk nut replacement. - Triumph Forum: Triumph Rat Motorcycle Forums
Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 22 (permalink) Old 08-13-2019, 08:41 AM Thread Starter
Supersport 400
Main Motorcycle: Triumph Bonneville T140E
Member
 
Boggie's Avatar
 
Join Date: May 2019
Location: Buckinghamshire, UK
Posts: 97
Head bearing top yolk nut replacement.

Hi all,

I would like to replace the cap bolt securing the top yolk to steering stem on my T140e. The existing item is old and a little rusty, complete with a push-on black plastic cap, which has split.

Rather than simply get a new plastic cap to hide the unsightly bolt, I was considering one of these:
https://www.triumph-spares.co.uk/ste...971-on-97-4317

Please excuse my ignorance but my previous experience, of more modern bikes, is that there was a nut/locknut to set the bearings on the steering stem, then the top yolk was attached/clamped independently of the nut. However, according to the drawings I am looking at, the T140e steering stem tube nut/cap provides both bearing set and yolk attachment (and as it is a tube nut with splits, the top yolk can clamp through it onto the stem):

https://nvt-motorcycles.com/en/trium...-forks-1979-81

I have 3 questions please:

1. As my yolks are already attached and ll clamped up with the bearings correctly set, will I be able to simply unclamp the existing nut, remove it and replace with the new chrome nut, then clamp it back up? Obviously I will need to check for any head bearing stiffness or play, then ride her and recheck but is it that easy?

2. Shouldn't there be a washer between the bolt and the yolk, rather than the nut acting directly upon the yolk paint? I can make or buy one (1" ID, 1+3/8" OD) but there is no washer shown in the illustration.

3. Is there a way to grease the top and bottom head bearings without removing them? Has a quick look before bed last night but didn't spot any grease nipples and don't have the owner's manual to hand.

Thanks,
Ian
Boggie is offline  
Sponsored Links
Advertisement
 
post #2 of 22 (permalink) Old 08-13-2019, 12:28 PM
wol
Moto Grand Prix
Main Motorcycle: T140 "special"
Senior Member
 
Join Date: Oct 2010
Location: Carmarthen UK
Posts: 2,547
Other Motorcycle: 1970 T120R Project
Extra Motorcycle: yes please
1 -- yes you can just replace the nut - but as you say - you will need to re-set the bearing

2 -- there is no washer - there is no need for the nut to bear down on the top yoke - it can sit proud of the top yoke - the top yoke is fixed when the pinch bolt is tightened onto the nut

3 - no - you have to remove the top and bottom yoke to grease the bearings
wol is online now  
post #3 of 22 (permalink) Old 08-13-2019, 12:54 PM Thread Starter
Supersport 400
Main Motorcycle: Triumph Bonneville T140E
Member
 
Boggie's Avatar
 
Join Date: May 2019
Location: Buckinghamshire, UK
Posts: 97
Thanks Wol,

Re #2: Doh, of course it doesn't... I should have realised that! 🙂 However, on mine, the existing nut looks like it is against the yolk. I wonder why....

Re #3: That is therefore a job for the winter strip down and makeover. I will replace the bearings when the frame comes back from powder coating.
Boggie is offline  
 
post #4 of 22 (permalink) Old 08-13-2019, 02:16 PM
Team Owner
Main Motorcycle: T160
Moderator
 
Join Date: Oct 2011
Location: Great Britain
Posts: 5,993
Other Motorcycle: T100, T150
Lightbulb

Hi Ian,

Quote:
Originally Posted by Boggie View Post
However, bear in mind a chromed one will go rusty at some point; fwiw, I've fitted polished stainless ones.

Quote:
Originally Posted by Boggie View Post
my previous experience, of more modern bikes, is that there was a nut/locknut to set the bearings on the steering stem, then the top yolk was attached/clamped independently of the nut. However, according to the drawings I am looking at, the T140e steering stem tube nut/cap provides both bearing set and yolk attachment
Quote:
Originally Posted by Boggie View Post
on mine, the existing nut looks like it is against the yolk. I wonder why...
Uh-uh, steering stem nut doesn't do yoke attachment. Your bike's steering stem nut is "against the yoke" because the forks parts aren't adjusted correctly:-

. Top yoke should sit on the top steering bearing dust cover. It should be held in place by both yokes' attachments to the stanchions.

. The steering stem nut is through the top yoke and the top steering bearing dust cover to bear on the top steering bearing itself.

. With the top yoke on the top steering bearing dust cover, even when the steering stem nut is on the top steering bearing, there should be a gap between the top surface of the yoke and the underside of the steering stem nut hex. This gap ensures that, when the steering stem nut is turned, the only friction is the steering bearing adjustment, never the friction of the nut rubbing on the yoke.

. When the steering stem nut is turned clockwise, because the thread is on the stem but the bottom of the nut is on the top bearing, because the bearing is conical and 'narrow end down', the bottom yoke (attached to the stem) is pulled upwards. The bottom yoke moving upwards pushes the bottom steering bearing upwards; because that bearing's also conical but 'narrow end up', turning the steering stem nut clockwise increases the friction in both bearings (and risking labouring the point, turning the steering stem nut anti-clockwise decreases the friction in both bearings).

. The top yoke pinch bolt around the steering stem nut is just to keep the latter in the position set by bearing adjustment; again risking labouring the point, the steering stem nut has nothing to do with keeping the top yoke in place.

. Asides:-

.. Once the top yoke is correctly sat on the top steering bearing dust cover, because turning the steering stem nut moves the bottom yoke, only the bottom yoke stanchion clamps must be loosened before adjusting the steering bearings, and tightened again after adjustment is completed.

.. Especially when turning the steering stem nut clockwise to tighten the steering bearings, ensure the headlamp shrouds (because they're between the yokes) aren't stopping the bottom yoke moving up.

Quote:
Originally Posted by Boggie View Post
1. As my yolks are already attached and ll clamped up with the bearings correctly set, will I be able to simply unclamp the existing nut, remove it and replace with the new chrome nut, then clamp it back up?
Normally, yes. However, as your bike's top yoke isn't in the correct position (sitting on the top bearing dust cover), when you fit the new steering stem nut, you'd be wise to move the stanchions through the bottom yoke, and thus the top yoke downwards away from the steering stem nut hex. Fwiw, having loosened the bottom yoke stanchion clamps, stanchions will likely still need to be 'persuaded' through the bottom yoke clamps ... I use a piece of wood on to the top yoke and belt the other end with a hammer, alternatively close to each stanchion. Having set the top yoke correctly, fit the new steering stem nut and check the steering bearings adjustment.

Quote:
Originally Posted by Boggie View Post
2. Shouldn't there be a washer between the bolt and the yolk, rather than the nut acting directly upon the yolk paint?
To amplify Wol's post, no. Because, as I say, there should correctly be a gap between the yoke and the steering stem nut hex.

Quote:
Originally Posted by Boggie View Post
3. Is there a way to grease the top and bottom head bearings without removing them?
'Fraid it's as Wol posted ...

Hth.

Regards,

Stuart
StuartMac is online now  
post #5 of 22 (permalink) Old 08-14-2019, 01:15 AM
Site Supporter
SuperSport
Main Motorcycle: 1970 Triumph Bonneville
Lifetime Premium
 
Code Man's Avatar
 
Join Date: Jan 2013
Location: Pollock Pines, CA, USA
Posts: 1,032
Other Motorcycle: None at this time
Thanks wol and Stuart! Just went and looked at my bike and the nut is tight against the top yoke. So the way I understand it Stuart, I'll need to loosen the two clamping bolts in the bottom yoke holding the stanchions and the clamping bolt in the top yoke holding the stem nut and tighten the stem nut. That should bring the stem up....right?
Code Man is online now  
post #6 of 22 (permalink) Old 08-14-2019, 03:18 AM
wol
Moto Grand Prix
Main Motorcycle: T140 "special"
Senior Member
 
Join Date: Oct 2010
Location: Carmarthen UK
Posts: 2,547
Other Motorcycle: 1970 T120R Project
Extra Motorcycle: yes please
not quite -- as you say , loosen the bottom yoke pinch bolts ant pinch bolt on the stem nut - make sure the front wheel is off the ground (it only needs 1/8 inch or less) -- then the fork legs and top yoke must be persuaded down to give the clearance between the top yoke and the stem nut flats

--- the bottom yoke must stay where it is because it is held in correct bearing adjustment by the stem nut

---- in effect you need to slide the top yoke down the stem nut slightly taking the fork legs with it and at the same time the legs slide slightly through the bottom yoke
wol is online now  
post #7 of 22 (permalink) Old 08-14-2019, 03:23 AM Thread Starter
Supersport 400
Main Motorcycle: Triumph Bonneville T140E
Member
 
Boggie's Avatar
 
Join Date: May 2019
Location: Buckinghamshire, UK
Posts: 97
Quote:
Originally Posted by Code Man View Post
Thanks wol and Stuart! Just went and looked at my bike and the nut is tight against the top yoke. So the way I understand it Stuart, I'll need to loosen the two clamping bolts in the bottom yoke holding the stanchions and the clamping bolt in the top yoke holding the stem nut and tighten the stem nut. That should bring the stem up....right?
Hi Codeman I can see why came to that misunderstanding, all the info is correct but the resolution is unclear.

As I understand it, the top nut controls load on both bearings, by initially pushing down on the top bearing as it is tightened then pulling up the steering stem into the lower bearing.

If you were starting from scratch, say after fitting new bearings, you would set the bearings first, then fit/clamp the top yolk to the stem against the top bearing dust seal, then fit/clamp the forks.

In our cases, it appears the top yolk may be too high. First check there is a gap between the top bearing dust seal and the underside of the top yolk. If there is you will need to loosen the top yolk steering nut clamp and the bottom yolk fork clamps. Next, get a block of hardwood and a lump hammer. Place the block on the top yolk next to one stantion and give it a hit with the hammer. This should move the fork through the bottom yolk a little. Then do the other side the same. Now check the gap between the top yolk and bearing dust seal. Keep going until the top yolk just touches the dust seal. Note, take it slowly, one small movement at a time. In my experience, it can take quite a whack to get the forks to move but start off light.

Once you are happy, check the steering head bearings are not too tight by turning the handlebars slowly from one side to the other, looking for tightness. Also check the bearings are not too loose by pulling/pushing your bottom of the forks forward/backward and feel for play. These should not have been affected but it is worth checking and adjusting if necessary, whilst everything is unclamped.

Lastly, tighten the lower fork clamps and top yolk bearing clamp to the correct torque. Double check everything and take her for a good long ride. Recheck torque when you get back.

Ian

Last edited by Boggie; 08-14-2019 at 03:37 AM. Reason: Correct autocorrect
Boggie is offline  
post #8 of 22 (permalink) Old 08-14-2019, 03:43 AM Thread Starter
Supersport 400
Main Motorcycle: Triumph Bonneville T140E
Member
 
Boggie's Avatar
 
Join Date: May 2019
Location: Buckinghamshire, UK
Posts: 97
You beat me to it Wol, spot on! 🙂

One last thing Code Man; only adjust the steering head bearing nut if you need to (feeling tightness or play in steering). This operation should not affect the bearings at all.
Of course there is the possibility that the top yolk is already on the top bearing dust seal and there is a small gap between the bearing nut and the top yolk. I didn't check with my feeler gauges but from what the guys above say, it does sound like the yolk is set wrong.
Boggie is offline  
post #9 of 22 (permalink) Old 08-14-2019, 04:30 AM
Team Owner
Main Motorcycle: T160
Moderator
 
Join Date: Oct 2011
Location: Great Britain
Posts: 5,993
Other Motorcycle: T100, T150
Hi Ian, Gary,

Mmmm ... yeah ... sort-of ...

Quote:
Originally Posted by Boggie View Post
As I understand it, the top nut controls load on both bearings, by initially pushing down on the top bearing as it is tightened then pulling up the steering stem into the lower bearing.
The steering stem is a sliding-fit through both bearings; however, the stem's an interference-fit in the bottom yoke so, when the stem nut's tightened, the stem's pulling up the bottom yoke, and therefore the bottom bearing, towards (just) the top bearing.

Quote:
Originally Posted by Boggie View Post
In our cases, it appears the top yolk may be too high. First check there is a gap between the top bearing dust seal and the underside of the top yolk.
Risking stating the obvious, if there isn't a gap between the top bearing dust seal and the underside of the top yoke and the top surface of the yoke is against the underside of the stem nut hex., there's at least one other problem ...

As long as there is a gap between the top bearing dust seal and the underside of the top yoke ...

Quote:
Originally Posted by wol View Post
make sure the front wheel is off the ground
Quote:
Originally Posted by Boggie View Post
loosen the top yolk steering nut clamp and the bottom yolk fork clamps. Next, get a block of hardwood and a lump hammer. Place the block on the top yolk next to one stantion and give it a hit with the hammer. This should move the fork through the bottom yolk a little. Then do the other side the same. Now check the gap between the top yolk and bearing dust seal. Keep going until the top yolk just touches the dust seal. Note, take it slowly, one small movement at a time. In my experience, it can take quite a whack to get the forks to move but start off light.
Aside, the wood doesn't need to be "hardwood", I use any old bit of wood handy; in fact, there's an argument for using softwood because you're less-likely to damage the yoke paint when you hit the other end of the wood with the hammer?

Quote:
Originally Posted by Boggie View Post
Once you are happy, check the steering head bearings are not too tight by turning the handlebars slowly from one side to the other, looking for tightness. Also check the bearings are not too loose by pulling/pushing your bottom of the forks forward/backward and feel for play. These should not have been affected but it is worth checking and adjusting if necessary, whilst everything is unclamped.

Lastly, tighten the lower fork clamps and top yolk bearing clamp
... top yoke stem nut clamp ...

Quote:
Originally Posted by Boggie View Post
to the correct torque. Double check everything and take her for a good long ride. Recheck torque when you get back.


Quote:
Originally Posted by Boggie View Post
If you were starting from scratch, say after fitting new bearings, you would set the bearings first, then fit/clamp the top yolk to the stem against the top bearing dust seal, then fit/clamp the forks.
I wouldn't. Your way, having "set the bearings first", you'd have to remove the stem nut - potentially 'unsetting' the bearings - to fit the top yoke; also you haven't positioned the stanchions so, in fitting the top yoke and 'setting' the stanchions in it, you risk moving the lower yoke downwards again.

Fitting new bearings: having fitted them with dust covers and bottom yoke-'n'-steering stem, I would:-

. fit the top yoke and then the stem nut, the latter just loosely against the top bearing;

. fit the stanchions and 'set' them in position in the top yoke, including tightening the top yoke stanchion clamps;

. tap the top yoke downwards, so the stanchions slide down through the bottom yoke, 'til the top yoke's sitting on the top bearing's dust cover;

. then 'set' the bearings with the stem nut;

. finally, tighten the top yoke's stem nut clamp.

Hth.

Regards,

Stuart

Last edited by StuartMac; 08-14-2019 at 04:52 AM.
StuartMac is online now  
post #10 of 22 (permalink) Old 08-14-2019, 08:06 AM Thread Starter
Supersport 400
Main Motorcycle: Triumph Bonneville T140E
Member
 
Boggie's Avatar
 
Join Date: May 2019
Location: Buckinghamshire, UK
Posts: 97
So, Code Man, to summarise Stuart's comments on the advice from Wol and Me to help you reset your top yolk: you can also use soft wood. 🙂
Boggie is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options
All posts must adhere to Forum Rules

Register Now



In order to be able to post messages on the Triumph Forum: Triumph Rat Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter your valid email address, that can receive an automated confirmation message. Otherwise, you won't be able to gain full access.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome