View Full Version : Front end chatter
Since i've put the gixer front end on, and rejetted the carbs i've noticed that under very hard acceleration or 80 + mph i get some front end chatter.
I've a diablo on the front 120/70 and a Bt020 on the back, standard chain n sprocket, it's prob a little old 2 years+
I've a Zx10r on the back also from last year.
While i'm putting it down to suspention set up for the moment i'd just like to hear a few other idea's as to what could be causing this.
So when the suspension is unloaded it's talking to you...
What does it do when it's loaded into a bend or when braking hard?
Well thats one way of describing it alright, i found this article earlier
"First we need to determine if the head shake is occurring during acceleration or de-acceleration (chopping the throttle)
If you find the front end skipping or wandering (seems to be searching for traction) and or starting to swap while under acceleration, you will normally need to add rebound (turn in) or reduce your compression 2 clicks"
Think i'll take her to the pro's and se what they can do with it, the back squats a little also i've noticed on bumps
custard
26-07-09, 06:20 PM
any chance you can post the article up chap?
and is that front or rear comp/rebound?
Front i assume
Here's the article's link
http://www.gpssuspension.com/tuning.html
custard
26-07-09, 06:58 PM
2.) Find large jump that tends to bounce the motorcycle after hitting it. If the rear end bounces up, add rebound. (Turn clicker in)
errrmmmmmmmm. might want to find a different article :)
yup.. rebound is to 'soft' (fast rate) which basically means that when you are going over a bump the rebound is letting the spring return to its 'relaxed' position to fast.
BTW.. compression and rebound is only the control of the spring, if the spring is not set up for the rider then no amount of comp+rebd adjustment will help.
compression and rebound. 'hard = slow movement' 'soft = fast movement' of the spring.
custard
26-07-09, 07:06 PM
could just be squatting at the back too much and lifting the front so it gets a bit of a weave on.
could also be the mismatched tyres...
Bit of a mash up, but even with the other tyre i had on when we first installed the front end it was chattering, I'd say it's the mix of suspentions, i know the ZX10r is stock setup for the ZX and Ter had the forks setup for this 750 when he was on the track with them, so there all prob way off for the SV.
I'm thinking it's time to give her to a pro and have him set her up for me .
custard
26-07-09, 07:30 PM
yeah that could be a plan. proly needs the sag and all sorts sorting - witchcraft obviously
btw is it chatter or weave?
21QUEST
26-07-09, 07:31 PM
Drag mate, I don't think a "Pro" is needed...well not yet anyways.
Just need to appraoch the sitution in a logical manner. It could indeed be front or rear causing it.....
First thing is to check everything is adjusted correctly/torqued up right. ie chain, Steering , wheels etc .
You said Ter had the forks set up for track....what exactly has bee done to them?....ask Ter.
Ben
how was the bike with the ZX shokky before the front end swap?
yeah that could be a plan. proly needs the sag and all sorts sorting - witchcraft obviously
btw is it chatter or weave?
Ummm define the diff there ?
Drag mate, I don't think a "Pro" is needed...well not yet anyways.
Just need to appraoch the sitution in a logical manner. It could indeed be front or rear causing it.....
First thing is to check everything is adjusted correctly/torqued up right. ie chain, Steering , wheels etc .
You said Ter had the forks set up for track....what exactly has bee done to them?....ask Ter.
I'll get on to Ter so and ask him what way they were sprung or what springs are in there
Ben
how was the bike with the ZX shokky before the front end swap?
Fairly ok, i was suffering with front end bobbing on gear changes, going up gear i mean, and coming out of corner she would drift a little, and was a bit harsh over bumps.
custard
26-07-09, 08:29 PM
weave/tank slap - large handful and it snakes...
chatter = tyre skipping on the road surface.
if it runs wide on exit you need more rear compression.
try this
http://www.moto-racing.co.uk/Guides/motorcycleSuspensionSetup.htm#DAMPING
Ah ha, deffo not a case of a tank slapper, so we just have chatter, @ the moment she's solid in the corners, but i'l a little nervous about flinging her in to the corners as the hard acceleration on the way out shows the chatter, much like straight line acceleration chatter, road surface of course makes it better or worse
noob-saibot
26-07-09, 08:50 PM
Ah ha, deffo not a case of a tank slapper, so we just have chatter, @ the moment she's solid in the corners, but i'l a little nervous about flinging her in to the corners as the hard acceleration on the way out shows the chatter, much like straight line acceleration chatter, Irish road surface of course makes it worse
edited that there for ya, lol
Fudging irish roads, more like dirt tracks !!!
Fairly ok, i was suffering with front end bobbing on gear changes, going up gear i mean, and coming out of corner she would drift a little, and was a bit harsh over bumps.
have you checked that the lower bolt on the shokky is not fowling the dog legs? i had this and it caused all sorts of trouble...
another thing is, if the rear of the bike is higher than standard and you have put a GSXR front end on which is lower than standard then its going to be very twitchy and unstable at high speeds. also very sensitive to handlebar input.
click the rebound up a couple on the front and see how it goes.. i know mine had a really bad weave at about 80ish because the suspension was to 'soft' (more reactive less damped) at the front.
have you checked that the lower bolt on the shokky is not fowling the dog legs? i had this and it caused all sorts of trouble...
another thing is, if the rear of the bike is higher than standard and you have put a GSXR front end on which is lower than standard then its going to be very twitchy and unstable at high speeds. also very sensitive to handlebar input.
click the rebound up a couple on the front and see how it goes.. i know mine had a really bad weave at about 80ish because the suspension was to 'soft' (more reactive less damped) at the front.
I know the bolt was close to the dog bones when we fitted it, but i dont think it's catching on the bones, i'll see if we can check it over the comming days.
i've a 120/70 on the front so , it's ment to be the closest to the stock front end.
custard
27-07-09, 11:13 AM
oddly - you may find you have too much rebound on the front and the forks cant extend quick enough so they pump down and then bottom out which causes the chatter. conversely this may be not enough compression...
but hey if its fine going in, just get the front wheel off the ground on the way out - hey presto no more chatter :)
oddly - you may find you have too much rebound on the front and the forks cant extend quick enough so they pump down and then bottom out which causes the chatter. conversely this may be not enough compression...
but hey if its fine going in, just get the front wheel off the ground on the way out - hey presto no more chatter :)
Fully you should mention this, i'm prob 14 + stone @ the mo and i've never come close to getting the front to lift on her, even now with the 160/162.5 jets.
Must not be dumping the clutch enough at high rpm
custard
27-07-09, 04:47 PM
keep trying :)
have you set the sag for your weight?
The back sag was set yup, and the front end is a bit more then 10mm left of travel, i'll sort that soon enough
custard
27-07-09, 05:37 PM
hmmmm... have just been trying to sort mine out so here are the could be's as i see it
could be the mis matched tyres.
could be too much front rebound so forks arent extending quick enough (bounce the front end and see how quick they come up, more than a second is too much i think)
too little rear compression so rear squats and front comes up (may exacerbate too much front rebound)
What if i cant bounce the front, i.e it's really stiff, and only moves a mm or three :S
are you sitting on the bike with the front brake on while you are trying to bounce it?
put a cable tie on the stanchions and take the bike for a blast, then come tell us how much it is travelling down the stanchions.
Post sat evening spin, about 80 + miles
http://photos2.pix.ie/4A/68/4A68F833B30240DAAD24B7E2423E0AAE-240.jpg (http://pix.ie/davewarrington/1125333)
sorry about the glare ..
custard
27-07-09, 09:17 PM
no idea. im out. other than stronger springs :)
oh and the reboud compression and tyres.
buy an r1, i have no idea :D
ok, the travel on the forks looks good so the spring is about the right setting. so if you are sitting on the bike and you cant move the front end by bouncing it then your compression setting has to much 'H' (not reactive enough) turn the compression 2-4 clicks to the 'S' (more reactive) then take it for another spin. if you feel that the front is to 'plush/wollowy' turn the compression to the 'H' 1 click at a time if it still feels to 'hard' then dont be scared to turn it further to the 'S'.
once you have your compression set then you can set your rebound.
Compression is on top right ? when i sit on the bike witht he brakes pulled, i can push the forks down, but it's not really much @ at all, i'll see if i can get a video of it 2 morrow maybe .
nope.. compression is slot/screw at bottom of forks. rebound is slot/screw on the top in middle of preload nut.
I'll adjust the compression this afternoon after i get a video of what she's like already
ooohhh, one other thing. did you balance the new front wheel?
Yes, the new wheel has been balanced when the new tyre was fitted ;) had that thought my self actually.
Spoke to a chap who does suspension, says he'll take a look on thursday nite, he was fairly hesitant when i told him it was an SV with a Zx10r rear and gsxr front, he wanted to know oil levels and spring rates, while i have that info for the back shock
99-02 SV650 337mm 510#
04 ZX10R 338mm 540#
Neither I or Ter know whats springs or oil are in the front, and it costs dollars to open them and have a look, dollars i dont rly want to spend .
So anyway, he said bring her down, we'll set her up to a good base setting and run her on the machine ( no idea what machine this is ) and see what we get.
I'd be happy enough just getting the chatter out of the front end, anything else is a plus
good stuff.. i'm sure that he will help in getting a start for you.
Yea hopefully, be interesting to see what this machine he has for the springs, seems it works out what they are weighted for ??
svdemon
28-07-09, 04:47 PM
Did you add the magnets for the speedo befoore you got the wheel balanced?
Did you add the magnets for the speedo befoore you got the wheel balanced?
I did yes, and i mentioned to the nice man who was balancing it that there is magnets on that side of the disc, so be stuck some weights on either side of it it seems ....
another thing (your not going to like it) you say that you were getting chatter/shake before the front swap when you were shifting up gears... have you ever thought that its 'user input'. i'm not trying to be funny or slag your riding m8, its just that a lot of people do it without realising what they are doing e.g. gripping the bars to tight shifting there hip to much, etc.etc. how is the chatter when you accelerate normally (rolling on the throttle rather than whacking it on)?
No no, my bad, no chatter with the old front end, she was solid as a rock, what i used to get was a lot of front rise, or a bobbing effect, change up gear, nose goes down, then back up, but that not the case any more.
Standard acceleration, is fine, no chatter, she can be bumpy over bumps, and in some cases very bumpy
svdemon
28-07-09, 05:01 PM
Sounds like too much compression/rebound damping to me. What weight oil did you use?
Biker Biggles
28-07-09, 05:03 PM
Sounds a bit like your new front end is set up rock solid.Either very hard springs or,more likely,wrong viscosity or too much fork oil or too much damping.
Biker Biggles
28-07-09, 05:04 PM
Ah the joys of synchronised posting---See SV demons post above.
Sounds like too much compression/rebound damping to me. What weight oil did you use?
Sounds a bit like your new front end is set up rock solid.Either very hard springs or,more likely,wrong viscosity or too much fork oil or too much damping.
I'd says he's just set up to hard really, i can push the forks down, while the brake is pulled.
I guess it's more along comp/rebound. we'll see what the setting show on thursday
P.S no idea of the oil weight
svdemon
28-07-09, 05:12 PM
Try taking all the comp/rebound adjustment off so its right round at "s" then see what its like. If that doesn't make it soft enough i'd be looking at changing the oil for some fresh 10w then you know where you stand.
I'll keep that in mind, it's lashn down here @ the moment, so no real test'n gonna happen today :(
custard
30-07-09, 11:21 AM
come on, put us out of our misery. what was wrong wi'it
Only back now, went off to get it done at about 6:30, hour and a half later and two forks dismantled, two washers removed and the springs inserted the right way up ( they were swapped over to extend the forks and add more preload)
Any what can i say, well i know how a train driver feels like now, cos this baby's on rails !!!!
No more front chatter, bumps are so much easier to handy, and in the corners :O lord it's like gliding around them now, all for the handsome price of 75 euro, money very well spent imo
excellent, would have never thought about the springs being wrong way up...
that was a very very good price m8....
the sv is a pleasure to ride with good suspension... they feel like a totally different bike and you can push them a lot harder.
Well the spring were in the wrong way around to alloow for the wasters to catch, and give it a 2 mm lift, again lenghtening the forks a little more, however rebound adjusters were off then, one has about 6 mm in travel and the other had 4, so over all a bit of a mess, shame i wont get out on it again now till tuesday :( damn weddings over the weekend means no more testing for me, but nxt weekend is my nxt dyno run, so hopefully i'll get the ok that she's fully jetted correctly also :D
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