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GS1000 tank slappers

  • Thread starter Thread starter gs79
  • Start date Start date
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gs79

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Took the 1979 GS1000E for some plug chop tests the other night. When getting upto speeds of 150km/hr the handlebars start to shake from side to side, so much so that it becomes unsafe. I have recently had a brand new front tyre which has been balanced. The steering bearings were replaced 8 months ago with a set of tapered bearings, steering brace fitted. Just wondered what you guys thought, would like to safely to get above 6k revs without risking a lock to locker.
 
check all the obvious. you say you have new front tyre and head bearings, so check rear wheel and swing arm bearings for play. make sure everything is tight on suspension and wheels etc.
if you cant find anything obvious, fit a steering damper. it will make your bike feel so much different during high speed cornering or blatting it through the twisties....
 
Have the shocks been dialled in? That seems slow to be getting that kind of problem.

Does the slap start as a slow weave or is it fast?
 
tatu said:
Have the shocks been dialled in? That seems slow to be getting that kind of problem.

Does the slap start as a slow weave or is it fast?
Click to expand...
that is just over 90MPH. hardly slow for a GS....... tank slappers can occur at half that speed in some situations
 
It starts as a slow weave at around 85mph then gets more pronounced from 90 to 95mph so much so that it is unsafe.
 
have you checked tyre pressures? try altering them slightly front and rear, see if it makes any difference
 
Was there a time when she was stable at 150 ?
Where did that fairing and fender come out of. I'd be inclined to whip one or both off and see what happens.
Is that a TKV 11 on the front.
 
You could try lowering your triple down your forks about a 1/4 in -5mm or so, I had a similar problem on my Roadkill bike and that took care of it. If you use a dampener you are just disguising the problem
 
Brendan W said:
Was there a time when she was stable at 150 ?
Where did that fairing and fender come out of. I'd be inclined to whip one or both off and see what happens.
Is that a TKV 11 on the front.
Click to expand...

I would try this first, and make sure that your rear end is dialled in right, the ohlins on the back of my bike were the cause of what you describe till they were set up when I first rebuilt the bike.
 
Will double check the tyre pressures, and tighten those steering head bearings, she's now running on Avon Roadriders. Will consider after checking everything out the lowering of the triple 5mm. Not sure what you mean by dialling in your rearend if you could please elaborate.
 
gs79 said:
Will double check the tyre pressures, and tighten those steering head bearings, she's now running on Avon Roadriders. Will consider after checking everything out the lowering of the triple 5mm. Not sure what you mean by dialling in your rearend if you could please elaborate.
Click to expand...

By dialling in I mean setting rebound and damping rate etc,they are adjustable?
 
If you have the air forks make sure that the pressures are the same. You should also check the fork oil and make sure that both forks are filled equally. My previous 1000 did the same at about the same speed until I found that one fork had leaked all the air out while the other was still at about 11psi.
 
Several questions in my mind as i've been involved with several race and a lot of road GS1000's, and generally, they don't weave, in fact they're a byword for stability.

Yes, it could be an aerodynamic weave - is that fairing frame or fork mounted ? I've seen fork mounted fairings make a bike very unstable.

tyres - generally the main reason for a weave. A lot of modern tyres have carcases which are not suitable for our old dinosaurs. A mismatch front to rear in tyre profile will cause weaves...

Mechanical - alignment first, then wheel bearings, fork bearings front and rear. Yes, fork leg imbalance can cause it, shocks not so much except if the swingarm bearings are shot too.

Don't drop the triple clamps down the forks until it's stopped weaving - you're reducing trail which will make it more unstable...Run the fork legs level with the top triple clamp

Yes, a damper will help - but our race GS1000 is set up to run straight and true without one and it's only there to restrain the front on bumpy surfaces - we run on street circuits several times a year.
 
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