Bike weaving at speed

(RIP) drillam

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I bought year 2000 R1150GS off a site member the weekend before last and rode it the 140 miles home, mostly motorway.

As I hit the M25 and took it up to around 75 it started weaving around a bit, like it was going to go into a tank slapper.
Promptly shit meself and slowly backed off the throttle. Back down to 65ish and it's fine. Eased it up again to around the 75 mark and it happened again, and again.
Eventually held the bars and my arms rigid and rode through it to just over the 75 mark and it settled down.
Every time I hit 75 the front end seems to go light and floppy, also happened a couple of times on fast bends with rough surfaces/tar banding.
Dunno if it's the tyres or maybe head bearings, but my other two GS's were rock solid on all surfaces at any speed.

Other than that I'm very happy with the bike.
It's fitted with Karoos, they'd done around 500 miles.

I never used Karoos before, but have ridden TKC's through a couple of winters on a previous 1200 and found them very confidence inspiring.
So what do you reckon? somebody suggested wheel balance, I'm thinking head bearings.
Any ideas please?
 
Head bearings should be pretty straight forward to check but I would guess wheel balance, or a duff tyre more likely. Check the rim is running true also. I had a similar problem some years back with Tourance front tyre which I replaced and the problem disappeared. Hope it's something as simple as that.
 
drillam said:
I bought year 2000 R1150GS off a site member the weekend before last and rode it the 140 miles home, mostly motorway.

As I hit the M25 and took it up to around 75 it started weaving around a bit, like it was going to go into a tank slapper.
Promptly shit meself and slowly backed off the throttle. Back down to 65ish and it's fine. Eased it up again to around the 75 mark and it happened again, and again.
Eventually held the bars and my arms rigid and rode through it to just over the 75 mark and it settled down.
Every time I hit 75 the front end seems to go light and floppy, also happened a couple of times on fast bends with rough surfaces/tar banding.
Dunno if it's the tyres or maybe head bearings, but my other two GS's were rock solid on all surfaces at any speed.

Other than that I'm very happy with the bike.
It's fitted with Karoos, they'd done around 500 miles.

I never used Karoos before, but have ridden TKC's through a couple of winters on a previous 1200 and found them very confidence inspiring.
So what do you reckon? somebody suggested wheel balance, I'm thinking head bearings.
Any ideas please?
Click to expand...

Do you still have your 1100GS ? if so swop the front wheels between bikes and ride both, see if the problem follows with the wheel.
 
With only 500 miles on them, have the sharp edges of the blocks worn down yet?

I've had weaving with new TKCs at speed until they've worn in a bit....you're actually riding on some ridge edges.

Slightly lowering the pressure can help.
 
Wapping said:
The beast in question: http://www.ukgser.com/forums/showthread.php?t=327051
Click to expand...

yup, that's the one, a wee cracker I have to say. I wasn't even looking for one.
I was happy to take the 1100 I bought from Steptoe back down to the Maghreb, but this came along.

The devil made me do it :D

Anyhow, thanks for all your replies so far.
I've consumed a wee touch too much vino colapso for the night :jager and will get cracking on your suggestions in the morning.
 
This feature could be handy on the approach to junctions where you suspect a SMIDSY.

;)
 
Well I found that the rear tyre valve was dodgy and had around 5psi. Replaced, pumped it up and took it up to Shaftesbury late yesterday afternoon. I ran 36psi front and 40psi rear on the Karoos, they have around 800 miles on them now.
I have Vern's panniers, Touratech top box, 90Kg rider, no pillion. Bike is a pretty standard 1150.
Hit 75 - 80 mark and the problem's gone, so didn't investigate any more. Carrying on with the journey and overtaking a Landrover at about 60+ on a fast B road bend, coming back in across the white line/cat's eyes, tar banding, and the front end tied itself in fukkin knots.
No real drama as it sorted itself out pretty quick, but slightly disconcerting just the same.

So I guess now I'll go back and check the things I was gonna check before I thought I'd cured it with the tyre valve.
Wheel Balance.
Head bearings.

Any other suggestions?
cheers
Millard
 
What are the shocks set at?

I find that if the rear preload is way too high the bike cannot react to surface changes and as you have described ties itself in knots!

Also check the front preload same again there It's even worse as there's no rebound damping

There are so many rice rocket owners that get a GS and automatically think that the suspension needs wound up to Max :blast :blast :blast

Millard not taking the piss but how much do you know about suspension setting? No point in me giving you pointers if you know old bean

Although the suggestion I'd make with the info at hand, I would set the preload just above Std (about 30% of what's available) Remember as well to unwind the rebound screw at the shock base and also set it to about 30% of it's range then try above or below 10% at a time until you achieve Enlightenment

Usually a GS upfront is fine with base setting or plus one on the front preload I'd only go higher with a passenger and a load

Hope that's all it turns out to be
 
Much appreciated Doc.
I know next to fekk all about modern suspension, having been reared on Hagon type shocks as fitted to the likes of Norton Commandos :nenau.

I had no troubles at all with my last two GS's so consequently suspension woes were not even on my radar for this one :blast

I'll have a look at that :beerjug:
 
Okay the rebound screw is on the exhaust side at the bottom

Fully in (Clockwise) is max

fully out (anti clock) is min

What I do is to count "half turns" You'll understand in a moment

Unwind it out fully and then screw it in all the way and count how many half turns in, I think it's usually 7 and a bit

Screw it out fully and then go about 2 and a half "half Turns" in for 30% approx

For the rear preload you should see the scale on the remote knob if you can't see the scale it's a maximum :blast

Unscrew it fully and then screw it in until you have passed "std" and if you are lucky you can judge where 30% would be

For the front there is a preload ring as per your Old timer shocks you want it to be on the lowest setting (longest spring) or the lowest plus one step

Let us know if that helps


Tyre pressure for Karoo is 2.5 (F) and 2.9 (R) bar, but I cannot see your initial setting of 40 psi rear being 2 psi less making that much of a difference
 
DrFarkoff said:
Okay the rebound screw is on the exhaust side at the bottom

Fully in (Clockwise) is max

fully out (anti clock) is min

What I do is to count "half turns" You'll understand in a moment

Unwind it out fully and then screw it in all the way and count how many half turns in, I think it's usually 7 and a bit

Screw it out fully and then go about 2 and a half "half Turns" in for 30% approx

For the rear preload you should see the scale on the remote knob if you can't see the scale it's a maximum :blast

Unscrew it fully and then screw it in until you have passed "std" and if you are lucky you can judge where 30% would be

For the front there is a preload ring as per your Old timer shocks you want it to be on the lowest setting (longest spring) or the lowest plus one step

Let us know if that helps


Tyre pressure for Karoo is 2.5 (F) and 2.9 (R) bar, but I cannot see your initial setting of 40 psi rear being 2 psi less making that much of a difference
Click to expand...

Once again Doc, thanks for taking the time.
I'll go through it all later today or maybe tomorrow and let you know what the settings were.
cheers
Millard
 
Front spring was one stop from the shortest setting, it's now on the 2nd from longest

Rebound screw was almost all the way it and the preload was down below STD. Both are now set as you suggested Doc.

Also the rear tyre lost 10psi since yesterday so that needs another look.
Head bearings are fine.
My guess is that it was a combination of bad settings/pressures and it's a case of fine tuning out the possibilities, so, almost there I'd say.

Thanks everyone for your help :beerjug:
 
Re tyre

an old squeezy bottle well rinsed out teaspoon ish of washing up liquid into bottle and a mug or so of water added (warm water is good at this time of the year :rob )

bloody good shake to get the foam going

Onto centre stand Mayeb tie stand to front wheel in case you bump it forward?? your call ??

Remove tyre valve and after letting the air out, squeeze contents into tyre (Squashing the tyre a wee bit with the valve opening open and then sticking the bottle at the valve stem and letting go of the squashed tyre and squeezing the bottle simultaneously is pretty quick) and refit valve and inflate

start motor

Pull in clutch select first and just "feathering clutch lever" (feathering stops the horrible driveline lash) enough to make the wheel spin for 30 seconds

Select neutral and Stop motor

and examine for Extreme foaminess issuing forth from an orifice or orifii :aidan


drillam said:
Front spring was one stop from the shortest setting, it's now on the 2nd from longest

Rebound screw was almost all the way it and the preload was down below STD. Both are now set as you suggested Doc.

Also the rear tyre lost 10psi since yesterday so that needs another look.
Head bearings are fine.
My guess is that it was a combination of bad settings/pressures and it's a case of fine tuning out the possibilities, so, almost there I'd say.

Thanks everyone for your help :beerjug:
Click to expand...
 
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