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Posted: Wed Aug 07, 2013 7:36 pm
by Gromit
We've linked to
this article on several occasions, but it's an interesting read (even if the technical stuff goes way over my head!!).
Posted: Wed Aug 07, 2013 9:03 pm
by boxerscott
fatnfast wrote:There should be no play when twisting/rocking the wheel at either 3-9 and 12-6 o clock.
If your certain its the paralever pivot bearings then you can adjust them without removing the bevel box. In fact you dont need to remove anything, but I would take the rear wheel off.
On the wheel side is the adjustable bearing. (The other side is fixed). You need to slacken and back off the large nut then adjust the central allen screw to remove the play. The manual says to torque this to 7Nm (please check, I think this is correct). In reality you need it tightned until there is no play.
If the big nut has never been removed from the factory heat it with a hot air gun to 'sizzle temperature', i.e the point that when you spit on it., it sizzles. This will melt the threadlock.
I removed all traces of old threadlock (nail varnish remover works well) and didnt put any new stuff back on. The nut has to be torque to 130Nm (check manual again), so its very tight. Put a blob of paint on it after to check its not moving.
Finally, you need to hold the central allen screw whilst torquing up the big nut. You can buy a cut out socket to do this from Laser Tools or make your own.
I adjusted my GS1150 at around 28k miles. Its done nearly 7k miles now and theres no play. If play does come back after adjusting, then its new bearing time Im afraid.
I dont recall reading anywhere of a case where they have failed big time and stopped the bike running.
Hope this helps.
It certainly does cos that's exactly where I am going to start.
Posted: Thu Aug 08, 2013 6:02 am
by Corvus
Corvus wrote:Gromit wrote:.......Certainly lends strength to the argument that input and output angles on the 2 UJ's should be equal though.
Absolutely. If my understanding of the theory is anything like correct, then the joints should be in phase and the input and output angles equal ie: parallel. ........
Is that the only "perfect" scenario for a hookes joint cardan shaft?
How about if the included angle at each end is the same, but the input and output shafts are not parallel. (And the actual included angle kept as near straight as possible and joints in phase, as before). Would this arrangement still cancel out angular velocity fluctuations? Dunno.
Surely, even if this "perfect" scenario is achieved, the intermediate shaft will still fluctuate, if I understand things half right. This in itself would cause vibrations of sorts. I'm sure the frequency could be worked out (by a man with scraggly hair, wild eyes and a white coat, obviously).
Judging by the number of equations on the link gromit mentioned, I'm sure there's a lot more to it than that.
Just a thought. Sorry!
Posted: Thu Aug 08, 2013 8:25 pm
by boxerscott
Now I`d best get me coat at this point.
Posted: Thu Aug 08, 2013 8:26 pm
by Gromit
boxerscott wrote:Now I`d best get me coat at this point.
I'll wait by the door, having already got mine.
Posted: Thu Aug 08, 2013 9:15 pm
by nab 301
Corvus wrote:Corvus wrote:[quote="Gromit.
Surely, even if this "perfect" scenario is achieved, the intermediate shaft will still fluctuate, if I understand things half right. This in itself would cause vibrations of sorts!
Yeah , it's called character....
Posted: Thu Aug 08, 2013 11:08 pm
by cornishflat
nab 301 wrote:Corvus wrote:
Surely, even if this "perfect" scenario is achieved, the intermediate shaft will still fluctuate, if I understand things half right. This in itself would cause vibrations of sorts!
Yeah , it's called character....
Thank goodness for that. I thought it was the twattin, playing up again.
Posted: Fri Aug 09, 2013 6:04 am
by Corvus
Quote: "Now I`d best get me coat at this point. "
And
Quote: "I'll wait by the door, having already got mine."
Aww. Shame. It's my round.
Quote: "Yeah , it's called character.... "
Couldn't agree more.
The twattin is the little circlip holding the UJ on. Obviously. Apparently they do play up.
Posted: Fri Aug 09, 2013 6:09 am
by Corvus
nab 301 wrote:Corvus wrote:
Surely, even if this "perfect" scenario is achieved, the intermediate shaft will still fluctuate, if I understand things half right. This in itself would cause vibrations of sorts!
Yeah , it's called character....
My point was.... Don't be too surprised if you feel a little cyclic thrumming! It's telling you you've been riding in a straight line too long.
Posted: Fri Aug 09, 2013 6:21 pm
by nab 301
The twattin is the little circlip holding the UJ on. Obviously. Apparently they do play up.
usually only when the shaft /UJ hasn't been hit home with a large enough lump hammer..
My point was.... Don't be too surprised if you feel a little cyclic thrumming! It's telling you you've been riding in a straight line too long. Very Happy
I wonder could that be fine tuned out with an adjustable paralever arm ?
Posted: Sat Aug 10, 2013 6:47 am
by Corvus
Quote: "I wonder could that be fine tuned out with an adjustable paralever arm ?"
Well it would alter the angle. As well as other things, including the design life of the UJ joint bearings. How it will alter the way things feel with reference to vibrations, the only sure fire way is test it. Lets face it, to predict with certainty how something will feel in a particular chassis, mixed in with other shake, rattle and rolls is surely impossible. For anyone.
In spite of what you may think given my above posts, i'm not one to complain too much about the odd bit of shaking and vibrating. It makes you feel that you are on a machine. Character. Who wants a bland machine?
But then I'm speaking as someone who these days mainly rides for pleasure, so I tend to find myself on roads that twist and turn, go up and down. You don't get much time to think about any particular vibration or thrum, unless it's acute. I suppose if I spent a lot of time on fairly straight, smooth roads I might have a different outlook?
On the subject of this cyclic resonance. Chain final drives are not exempt from this kind of thing.
Posted: Thu Aug 29, 2013 8:33 pm
by boxerscott
Righty Ho, thrumming aside, I have sorted the freeplay issue, after removal of rear wheel I slackened the paralever final drive bolt and with heat gun assistant then removed and cleaned lhs final drive pivot bolt, put it back in dry and wound her in to get a feel for when it contacts with uj, with slight increments until free play disappeared. Then I took it out and applied Super Novae seize lock and wound her back in until free play disappeared. Left it overnight and applied more thread lock to exposed thread and then torqued up 32mm back nut 105n/m. Re fitted wheel and tightened up paralever.
Deliberately did not torque up pivot bolt (9n/m) cos that is what I did 2 years ago when I re framed her. I am thinking that under torqueing is as bad as over torqueing in this instance and no wiggle must be the right torque
Fingers crossed.
Posted: Thu Aug 29, 2013 9:39 pm
by conkerman
I thought the Paralever adjuster pin was torqued to 10Nm, and the 7Nm was wrong.
Can't for the life of me remember where I found it though. The corrrect torque will essential for preloading the bearings.
Posted: Thu Aug 29, 2013 10:55 pm
by boxerscott
conkerman wrote:I thought the Paralever adjuster pin was torqued to 10Nm, and the 7Nm was wrong.
Can't for the life of me remember where I found it though. The corrrect torque will essential for preloading the bearings.
Correct Torque?
Shy Torque
I dunno, my bearings may be knackered then! I`ll soon find out on the mullerin` its going to get in Spain shortly
Posted: Fri Aug 30, 2013 7:16 am
by timbox2
boxerscott wrote:No not the wheel, the movement is at the final drive /swing arm interface.
I am thinking uj pivot bearings area. Its done 27k and it is 10 years old but I am not wanting catastrophic failure especially on our Spain Adventure later this year
So if I hold wheel at top and bottom I can get movement. I will take calliper off tomoz and see if I get more movement which would indicate a problem in the area you are talking about. There does not appear to be any movement in the 9 o clock to 3 o clock axis. The handling is fine, no wobbles, no shakes, no running wide no pulling to left or right under braking. No fluid leaks.
The cyclic resonance is hardly discernible, that could be me just being paranoid about every noise this MF makes
I had to replace the pivot bearings on my bike twice, both times the bearings had done about 25,000. I remember Steptoes tip for working out if its wheel bearing or pivot, needs another person though ideally. While somebody rocks the wheel, get your fingers between brake disc and FD, if you feel the gap changing, its wheel bearing, if not its pivots.