Straight-line Headshake

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bigdave139

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Firstly i should point out i know naff all about suspension settings etc, the bike is set exactly how i got it!

Whenever i give it beans in a straight line to the point where the front wheel is just going light, i get quite major headshake.

Makes no difference on surface, and i've tried all 10 clicks of adjustment on the damper.


Riding alongside my mates fireblade today, both flat out from about 30mph, he left me because i had to keep backing off :(

Is it suspension settings i need to be changing, or do i have a dodgy damper?!

cheers
Dave
 
Hi Dave

I suffered the same problem. I found it was because I was pulling on the bars too much under hard acceleration. Not saying that's what's happening to you but its easily overlooked.
 
Really? I'm not aware i'm doing it... i'll get out tomorrow and try it. if i am its for fear of getting fired off the back with the brutal acceleration! haha.
 
Really? I'm not aware i'm doing it... i'll get out tomorrow and try it. if i am its for fear of getting fired off the back with the brutal acceleration! haha.

Haha I know the feeling! Try keeping your weight forward using your feet, bum and legs as much as possible.
 
Haha I know the feeling! Try keeping your weight forward using your feet, bum and legs as much as possible.

yeh i'll give it a go, i'm still waiting for my new leathers to show up so i'm wearing kevlar jeans at the moment, my ass just slides back when i pin it. i know i'm not going to go off the back but its not a good feeling!
 
You should not have the damper very stiff at all. Ive not played with an adjustable OEM one, but to give you an idea my aftermarket one is set at 4 clicks (20 max).
 
You should not have the damper very stiff at all. Ive not played with an adjustable OEM one, but to give you an idea my aftermarket one is set at 4 clicks (20 max).

OK i'll put that back to where it was (center) before i go for a ride tomorrow!

Hi Dave, has it always done it, or is it something the bike has just started to do?

Its always done it, when i first got it i though maybe it was just me... and apparently it probably is!! :D
 
OK i'll put that back to where it was (center) before i go for a ride tomorrow!



Its always done it, when i first got it i though maybe it was just me... and apparently it probably is!! :D

I get it too mate and i know of other S1K riders that get it too and its not just a little weave here and there its proper slapper stuff, Having a death grip on it would cause it but myself and the other guys don't grip the bars like that and still get it.
Apparently the S1K was based on a K5/6 1000 GSXR funny thing is during my 4 years of ownerships of a K5 1000 GSXR i never... ever had anything like the headshake you get on a S1K.
 
The reason I asked if it's always done it, is because front end problems are usually caused by a problem at the rear. Head-shakes at certain speeds and riding conditions could be caused by something as simple as the rear wheel in need of balancing. If the rear is not balanced, it doesn't necessarily mean that you'd feel it wobbling as you ride along - it could feel totally fine until you build speed, accelerate hard etc.

Just thought I'd let you know about this odd trait... It might be something else completely, but you never know?!
 
Hi Dave

I suffered the same problem. I found it was because I was pulling on the bars too much under hard acceleration. Not saying that's what's happening to you but its easily overlooked.

This is exactly what is causing this imo. Your natural reaction under hard acceleration is to grip harder on the handle bars this then causes uneven pull on either left or right grip which in turn sets the front wheel in a different direction when its feathering the road causing a wobble....

Andy is spot on, when he says use your feet to push your weight forward under hard acceleration and exaggerate a loose grip on the handle bars....
 
What model bike is it and have you had it from new? If second hand it could be the previous owner has dropped the folks through the triple clamps to speed up the steering (or jacked up the back for the same result). If you speed up the steering you'll lose out in straight line stability. Would be worth checking the geometry of the bike is standard.
 
Not sure how much you weigh, but try an extra turn on your rear pre-load (increase) assuming you have left it at the stock setting. I weighed 90kg and I had the same problem. I found that with the slightly stiffer rear, it didn't affect the ride comfort, but reduced the rear dipping under hard acceleration. Bar wobble disappeared immediately, probably due to a better suspension balance.

I would recommend you get a couple of mates to help you measure how much free sag/static sag/rear suspension travel you have and tweak accordingly. The BMW manual gives you a rough starting point, but if you Google "Dave Moss Suspension" you'll find some very useful info and vids.
 
I thought that when I got the head shakes it was nothing to do with me. turned out when I had relaxed a bit it was not so bad and after having my suspension set-up its gone. That was the 2010, my 2011 I set the suspension up from day one and not had any issues, although a stiffer steering damper would not go amiss.
 
Thanks for all the help guys, I had a little run out yesterday and concentrated on exaggerating the relaxed grip and it does feel better, still get it on hard acceleration though.

I'll drag some mates round and have a play with suspension settings this weekend. How much wouli i be looking to get it done by someone that knows what theyre doing?!

Any recommendations?

cheers
Dave
 
Simon at SNS motorcycles in Ockley will do a basic front and rear end setup for 20 quid and also you get
to call him for support too. Very nice chap.
 
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