45 mph handlebar shake


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kndw
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45 mph handlebar shake

Postby kndw » Wed Sep 18, 2013 11:27 am



Hi all,

I've got a problem with my '76 GL1000. When I'm going around 70kph (40-45 mph), the handlebars start to shake. It feels like an up-down shake, not sideways. I believe that common causes of this problem are worn steering stem bearings, worn swingarm bearings, tire cupping, and worn shocks (front/rear).

The thing is, I rebuilt the bike in the last few months: replaced the front and rear shocks by new parts, put on new BT45 tires, and also replaced the bearings. I'm all out of ideas - any suggestions?

edit: I also had the wheel bearings checked and the wheels rebalanced (the mechanic said there was no unbalance that would be noticeable)...



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Re: 45 mph handlebar shake

Postby virgilmobile » Wed Sep 18, 2013 11:35 am

Was this shaking there before AND after all the work done to it.?

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Re: 45 mph handlebar shake

Postby virgilmobile » Wed Sep 18, 2013 11:40 am

Also,while its shaking,can you do anything to change it.
Eg,applying the front or rear brake without slowing down,swerving from side to side,using a bit more throttle or backing off,adding a passenger.??
Anything you can do to change it can help identify what is causing the shaking.

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Re: 45 mph handlebar shake

Postby kndw » Wed Sep 18, 2013 11:56 am

virgilmobile wrote:Also,while its shaking,can you do anything to change it.
Eg,applying the front or rear brake without slowing down,swerving from side to side,using a bit more throttle or backing off,adding a passenger.??
Anything you can do to change it can help identify what is causing the shaking.


Thanks for the quick reply!

The shaking occured/occurs before and after the rebuild. The shaking only occurs around 45 mph, so adding/releasing throttle with respect to that speed eliminates the wobble (regardless of the revs/gear).

Before the rebuild, the bike seemed more stable with a passenger, although i'm not 100% confident that it indeed was. After the rebuild, I haven't had a passenger yet.

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Re: 45 mph handlebar shake

Postby virgilmobile » Wed Sep 18, 2013 12:26 pm

Sounds like it's time for a test run....Not just to feel it shake,but to try different things to get it to change....
At the speed it vibrates at,and keeping it at that speed with the throttle,gently apply the front brake....keep the speed up there....If no change,do the same with the rear brake....
Shift your weight....move the bike from one lane to the next.
Add a passenger.
Something should affect it.
Handlebar shaking side to side is well documented but you sound like it's a vibration.

Forget about the engine....if it does this regardless of the gear your in(rpm)..and only at this one speed....

It's suspension related or drive line....remember it does have a "U" joint and rubber dampers in the rear wheel.
You would be looking at something that turns at the same speed(the vibration) regardless of engine rpm.
That would be...brake rotors,the entire drive line.etc...

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Re: 45 mph handlebar shake

Postby virgilmobile » Wed Sep 18, 2013 12:30 pm

I forgot to ask...the vibration...does it come on and off suddenly or is it a progressive thing..
Kinka like a little at 40...gets maxed at 45 and tapers off at 50...Or just starts vibrating like you turned on the Harley effect. :D

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Re: 45 mph handlebar shake

Postby WingAdmin » Wed Sep 18, 2013 12:54 pm

First ensure it IS coming from the front end.

Try gently putting the front brakes on and see if it changes. Then do the same with the rear brakes.

Try putting the front brakes on only, and use them to decelerate through 45 mph, to see if it still happens when the suspension is loaded up from deceleration. Then try accelerating strongly through 45 mph, to see if it happens when the front suspension is unloaded.

If you can get your eyes on it while it is happening, have a look to see if just the lower fork legs are moving during the vibration, or is the whole front end moving?

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Re: 45 mph handlebar shake

Postby kndw » Wed Sep 18, 2013 12:57 pm

virgilmobile wrote:I forgot to ask...the vibration...does it come on and off suddenly or is it a progressive thing..
Kinka like a little at 40...gets maxed at 45 and tapers off at 50...Or just starts vibrating like you turned on the Harley effect. :D


Lol - I've been imagining a harley must feel like this :D

The testing-paradigm you propose is quite rigorous - I need the weekend to do it properly. Keep you posted on the findings.

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Re: 45 mph handlebar shake

Postby virgilmobile » Wed Sep 18, 2013 2:36 pm

Im sure "we" can figure this one out....Keep us posted...

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Re: 45 mph handlebar shake

Postby kndw » Wed Sep 18, 2013 3:28 pm

virgilmobile wrote:Im sure "we" can figure this one out....Keep us posted...


I mean 'you guys', of course, anyway - thanks!

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Re: 45 mph handlebar shake

Postby kndw » Thu Sep 19, 2013 5:30 am

I couldn't wait, so I rode the bike to work this morning.

A few observations:
- the shaking occurs at a bit higher velocity than I thought (around 80 kph ~50mph?);
- the shaking isn't only up and down, but also sideways. I noticed when I let go of the handlebars just slightly;
- the shaking is most pronounced when i decelerate (eg from 90kph down to 70, being most pronounced at 80);
- applying the rear brake doesn't affect the shaking, applying the front brake may reduce the shaking slightly, although I'm not 100% sure;
- i did notice that the lower fork legs seem to shake.

As an aside, a fork brace is installed. I installed this earlier hoping that it might eliminate the shaking, but it didn't...

Maybe the head stem bearings aren't tightened with the right torque? Does anyone know how much this should be?

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Re: 45 mph handlebar shake

Postby kndw » Thu Sep 19, 2013 5:34 am

I've attached a picture of the bike, so you can see the kind of fork brace installed...

[img]
Motoren-28.jpg
[/img]
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76 GL 1000
76 GL 1000

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Re: 45 mph handlebar shake

Postby virgilmobile » Thu Sep 19, 2013 2:57 pm

OK...I have a few questions now....

put on new BT45 tires, and also replaced the bearings.


The bearings....the wheel bearings only or did this include the steering bearings..??
Did you mount the tire and balance it or "the shop"...???
Was the balance done on a balance frame or after it was on the bike.?.It really makes a difference.
Were lead weights attached to the spokes to balance it or did you use balancing beads inside the tire...?

replaced the front and rear shocks by new parts,

The "new "front shocks"....were they actually brand new or new to you(used)..??
Were the old forks bent.??This can also bend the triple tree frame...Had one like that...
Were the fork tubes inspected for being bent..??
When the new front shocks were installed...were they assembled on the triple tree and aligned for true before the slides were put on...?
Were the shocks checked for the dampening with the new oil..??
Do you have and "Stiction" problem with the front shocks....1/2" variance between full load/release and unload/release....where the shock rests at.....??
Was the steering bearings replaced and seated "by the book"....See attached...

Sorry for all the questions...because I'm not there to lay hands on it,I can assume nothing.
It's a step by step procedure on the front end...Once the steering bearings are OK and the forks are dead true level,assembled and tested properly,the last step is proper rim alignment(spokes) then tire balance.....
The service manual for this bike can be downloaded from the "Manuals "section.

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Re: 45 mph handlebar shake

Postby virgilmobile » Thu Sep 19, 2013 3:20 pm

Another question or two....
While riding below the vibration point..Does the bike track straight.?
If you lighten your grip,does it "pull" to one side..?
Do you have to keep some pressure on one side or the other to keep it going straight...Does it wander or feel wiggly going over ridges like a wheel is moving sideways...
Is the tire pressure up OK...Run the tires near the maximum pressure....
I think mine run well near 35 psi rear and 38 psi front....

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Re: 45 mph handlebar shake

Postby kndw » Thu Sep 19, 2013 3:59 pm

Thanks for all the questions - I really want to fix this!

I'll answer them one by one:

* The bearings....the wheel bearings only or did this include the steering bearings?
> The wheel bearing were checked by the shop; I put in new steering stem bearings myself.

* Did you mount the tire and balance it or "the shop"?
> The tire was mounted and balanced by the shop.

* Was the balance done on a balance frame or after it was on the bike? It really makes a difference.
> Balancing was done in the shop, on a balancing machine, with the tire mounted.

* Were lead weights attached to the spokes to balance it or did you use balancing beads inside the tire?
> lead sticky-weights were stuck to the rim.

* The "new "front shocks"... were they actually brand new or new to you(used)?
> The new shocks are springs. I ordered them new (some german brand - Wurth or something)

* Were the old forks bent?
> I have tried three pairs of (2nd hand) fork legs. Although there is no way of knowing for sure they were straight, there was no difference between either pair of legs.

* This can also bend the triple tree frame. Had one like that.
> I have tried two triple trees. Also no difference, but of course, either might be bent...

* Were the fork tubes inspected for being bent?
> The legs were not inspected.

* When the new front shocks were installed.were they assembled on the triple tree and aligned for true before the slides were put on?
> I put the bike on a lift and took out the fork legs, slid new ones in, replaced the springs and the oil, and then assembled the rest of the front (i.e. fender, brace, wheel).

* Were the shocks checked for the dampening with the new oil?
> Yes, by me. They seem to be responsive as they should.

* Do you have and "Stiction" problem with the front shocks....1/2" variance between full load/release and unload/release....where the shock rests at.....??
> I never noticed any stiction at any point.

* Was the steering bearings replaced and seated "by the book"....See attached...
! > No. I did not know of this procedure. I have now ridden about 300 kms - will the bearings already be worn by (possible) faulty assembly, or is it still worthwile to check proper torque?

* While riding below the vibration point.Does the bike track straight.?
> Yes. The bike tracks perfectly straight.

* If you lighten your grip,does it "pull" to one side..?
* Do you have to keep some pressure on one side or the other to keep it going straight...
> No.

> Does it wander or feel wiggly going over ridges like a wheel is moving sideways?
! > yes! When i pass over white striping in the road (which lies a slight bit higher than the road), it feels as though the frame is being wrung out like a towel, which is an overstatement, but should get my feeling accross...

> Is the tire pressure up OK...Run the tires near the maximum pressure. I think mine run well near 35 psi rear and 38 psi front.
* The pressure is at that level.

>>> It seems to me that the best course of action at this point is to properly mount the bearings in the steering stem. Do you agree?
>>> What does it mean when i feel the frame 'twisting' going over a slight ridge?

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Re: 45 mph handlebar shake

Postby virgilmobile » Thu Sep 19, 2013 5:15 pm

Thanks for the details.They will take me a while to consider.
I'm trying to imagine myself in your place while you ride the bike.
With the new details its now a bit easier to diagnose the problem areas
In the mean time,by all means do loosen and re-torque the steering nut.
You need to loosen the fork clamps at this time the secure when done.
Ill review your post and see what I can come up with that you may have overlooked.

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Re: 45 mph handlebar shake

Postby virgilmobile » Thu Sep 19, 2013 9:55 pm

Some movement when the front tire traverses a ridge is normal.Noticable but shouldn't make you pucker up and clench the seat.
If it is unnerving or great fear of loosing control of the bike,you'll want to look for a loose rear swing arm bearing,bent axle or any side to side play in either wheel.
A wheel can track perfectly front to rear and be tilted top to bottom.
Any movement in the bike and one wheel goes straight up and down,the other one at a slight pitch off center...the whole machine gets really hard to stabilize.
This is why I question everything.
Those darn front forks...if there not exactly installed,aligned,secured exactly right.there will be problems.
Keep in mind.Your riding on a heavy machine at 70 kmph balancing on 2 patches of rubber no larger than your hand.
Include with that the front wheel not only has to roll but it goes up,down and turns.
If there is the slightest misalignment,bad wheel bearing,fork slide bushing,wiggle,play or bad fitting,this machine will get hard to handle.
Every single suspension part must be torqued in the proper sequence and specs.
With these parts,often close just isn't good enough.
I also would question what you did not work on for the same reason.
Pull the front wheel,check the axle,roll each bearing and scrutinize it.
Roll the wheel suspended by ONLY the axle in the forks.Look at the rim for running true,spin it several times to be certain it dosen't stop in the same place.

Ill quit for tonight.I can tell when I start to ramble on and on.
Sorry..Virgil

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Re: 45 mph handlebar shake

Postby virgilmobile » Fri Sep 20, 2013 11:03 am

Here's yet more stuff to read....
the forks can easily be checked for being bent...Lay both forks on a block of wood.One at each end.
With a light underneath them,roll just one fork against the stationary one.Repeat for the other fork.
If either is bent,light will shine through.
The axle can be rolled on a piece of glass...

I did have a bent triple tree on a 83...On the bike,one fork slid through both mounts fine,the other side was slightly misaligned at the top...I had to force it to go in...I replaced it...

After the forks are mounted to the triple tree,secure the top clamp and snug the bottom ones,lay a piece of glass across the forks (slides still off).
The glass needs to be large enough to span the width and length of the exposed fork.
If they are perfectly parallel,the glass will touch evenly.If the forks are misaligned,the glass will have a gap at one end.
If there not parallel,I used a long piece of wood and another person to "twist" them straight.
Secure the bottom clamps ant check again....

The Teflon slide bushings....the lower one may need to be squeezed to keep the end gap closed before it's put on the fork...when the slide is test fitted there should be absolutely no side to side play..I did have a slide that was worn inside.Before I put in the spring,I could move the slide bottom front to back almost 5mm.

When assembled before the oil and spring is installed,operate the slide full stroke,checking for lateral play or sticking....Add the oil and stroke it a few times then check for hydraulic dampening on the down stroke...I did have a broken valve in a used fork....
Test each one separately..

Mount the tire...This is the odd part....before you tighten the cap nuts on the axle...lower the front end of the bike till the front wheel is almost at the end of the up stroke..***The springs are not put in yet***....Then secure the axle nuts....
This keeps the slide in the proper alignment/spacing/width..
Raise the bike and install the springs....

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Re: 45 mph handlebar shake

Postby kndw » Mon Sep 23, 2013 1:24 pm

Hi,

During the weekend, I tightened the steering stem bearings. This did improve handling at low speeds, but above 140 kph (~90mph), it feels like the bike's frame turns into rubber (overstatement).

I then took apart two sets of fork legs that were previously installed - the bike had the same shakiness while riding with those forks. I did not take apart the newly installed front end, because I need the bike to get around.

I rolled the fork legs on a glass plate, but didn't notice any bending on either fork leg.

However, on inspection, i did notice a particular kind of 'scratchy' wear on one side on the lowest part of all fork legs. See the attached image. Is this normal wear?

scratched legs
scratched legs


Also, I noticed that the fork springs that came out of those forks were worn unevenly: each pair had one member that was clearly shorter than the other, by about 5mm.

What do you make of this?

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Re: 45 mph handlebar shake

Postby virgilmobile » Wed Sep 25, 2013 4:34 pm

It looks like somebody had there way with it on a grinder trying to make it fit.....Download the service manual...it covers the wear limits...Here's a link to some more info....http://www.cmsnl.com/honda-gl1000-gold- ... F++10.html
Here's what they should look like...




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