Monster High speed wobbles

So I know this topic has been covered before and forgive me for not having the exact settings to hand but here's my issue...

I have an 08 which seems manically out of control at higher speeds under power.. it's starts with a gentle head shake and if I keep the power on heading past 80mph it gets more violent. Road conditions don't seem to make a difference ranging from bumpy to perfectly flat. I have dropped the forks through the triple tree as far as they'll go and run settings I've seen on posts here that work for other riders off similar weight, yet I still get scary head shakes soothed only by letting off the throttle a little but reappear once I get back on it. I've had the bike set up previously by a so called suspension expert for sag etc.

I'm about 170lbs running Bridgestone S20 tyres.. I'm not a super fast rider and not aggressive on the throttle... thoughts or suggestions?

That’s an unusual one as head shake usually gets worse when you roll off and settles down if you keep accelerating. This is not an SD specific thing but applies to all bikes or at least all the bikes I’m aware of. In fact the common route to a tank slapper is hard acceleration over a few bumps, some head shake, freak out and close the throttle and hey presto you have a tank slapper.

Mine is an 06 model on the track settings as listed in the manual. It shakes a bit at speed under hard acceleration, especially if cranked over and provoked by a rough surface but it never threatens to get really out of hand. I focus on a light grip on the bars (heavy grip can induce head shake) and accelerate through the problem as quickly as I can.

Somebody with more expertise than me might be able to give better advice but if you feel it’s safe to try then pin it for a bit longer than you have been, relax on the bars even if it shakes a bit and see if it all smoothes out a bit further up the speed range.

Good luck!

Dropped the fork's down,,,, fork angle is steep as it is (to steep IMO ),,,pushing the fork "down" (will raise it up in front) in the tree is the way to more stability,,,ala Nicols upper tree,,,

If you have different oil heights this will occur.

tyre pressure is critical, as jgaches suggested. If the tyre carcass is of the stiffer variety you will need to use even less pressure. I run F-30psi/R-31psi in my Q2s for the street (30/28 for the track).

Another thing to look at is the steering head bearings. If they are too tight or damaged from too many heavy landings from wheelies they can cause headshake issues. Get the front end off the ground and check bearings for looseness,being too tight or notchy feeling when turning front wheel side to side.

Too little sag can cause stability issues as well. Make sure the bike has proper rider/static sag.

Good luck.

echo-ing the sag suggestions.

i've pushed the tubes further down the triple clamps as well and that helped alot - i had a pretty nasty tank slapper going through some bumps at about 75mph . Haven't had any since .. I think the springs on my bike front are too heavy as i have the preload backed all the way out and the sag up front is at the very far end of the recommendations... Front of bike feels stiff so i'm currently looking into revalving the forks and possibly softer springs.

I also have the rear shock set so the preload NUT is backed off quite a ways ... anyway - it's too hard to type about .. But right now my bike corners evenly and balanced front to back and feels great - can lay the bike over as far as i know how to and just goes good !!!

I've also heard different brands of tyres can possibly cause shake.

cheers - good luck

hey guys.. thanks for the replies.. a few things to check out.. I was gonna do the fork oil pretty soon anyways so this will give me a chance to check headstock bearing and oil height... I forgot to mention when I have my 115lb g/f o. the back the damn thing behaves.. as for accelerating through the head shake... noooo fookin chance.. I have tried it a few times and I can assure it doesn't feel like it's gonna get better... I try to stay light on the bars but makes no difference.. she was un rideable today at speed on my favourite road...

double post.. doh

These are the basics things to check, as any one of them can give you the that dreaded weave

1. Check your wheels are in line
2. Tyres are a matched pair and not worn out (as said low pressure helps)
3. Fork Legs are Flush with yokes tops
4. Both Fork legs have the same settings......
5. Check your Sag ...
6. Go back to base suspension settings ......as badley mismatched setting can have this effect

Check wheel balance, out of balance wheel will produce these symptoms and the symptoms increase with speed.

I'm about 170lbs.. so no featherweight, the rear does feel hard to me but this was how an alleged suspension expert set it up... I'm not the original owner but have had it since 1200 miles.. I'm gonna do as suggested and return to manufacturers settings... can you guys confirm I screw all adjustments in fully then back them out to the relevant number of clicks?
Thanks for all the suggestions fellas.. much appreciated..

All the way in clockwise then out the number of clicks

Can you read the numbers on the rear spring? The p.o. might have swapped it for a stronger one.

Yep. Wind them all in clockwise and then back off the number of clicks per the handbook - check under the seat as the settings should be there for easy reference. Good luck.

its all in the handbook.... [/quote]

RTFB eh... read the fookin book..

Alas I'm working till the weekend and can't get to her till then but thanks again guys and I'll post my results thanks again

man ive accelerated hard up to 140 several times and other then wind tugging at my arms and transferring it to the bars ive felt nothing, stable as a rock for me!

Stratkat.. can you give me some specifics.. ie.. your set up.. tyres your running.. your weight etc..

Ok kids.. here's the update.. forks dropped threw the triple trees about an 1/8 inch.. settings al back to basic per the sticker on my seat.. checked my headstock bearing while I was at it.. all good.. test ride reveals some fuggin problem and this was just accelerating down an on ramp.. not bumpy neither...

Up next is wheel alignment..

It’s not sexy, it’s not MotoGP, it’s not degrees or caster, it’s not dark art....but back to basics, as I posted before.......................

Check wheel balance, out of balance wheel will produce these symptoms and the symptoms increase with speed.

Get the wheel balanced, if the problem persists, back to the dark art.

I am no suspension expert and mine started shaking its head at around 90-110 when accelerating hard so I got the rear sag set up, but because they are stiff to start with we had to reduce the rear height. So to keep bike level I dropped the forks through the yokes by 10mm and took off all preload. I use the halfway point between track and standard settings on rebound and high/low compression front and rear and now seems very stable. I weigh around 11.5 stone and only do medium to fast road riding.

I took off the front roughly what I took off the rear as getting the right sag was a bitch as WP use quite stiff suspension. surely that would even itself out wouldnt it?. I thought before it was a little hesitant to turn into a corner and then I ended up running wide on the apex/exit.

The fork legs were flush with the top of the triple clamp and thats when I felt I had to push it into corners and felt it was running wide. now it runs into corners with very little effort and as I dont do any track riding I never get to push it too its limits. I may during the week try and get them back through which might be trickier than it looks.

I think we got a classic case of thread thievery going on here. Where in hell did that little cheese thief?
Hey Jr. you got to watch for the bait and switch or you'll be moving forks up and down in triple clamps all day long. Looks like mission impoosible pulled the wool over all you helpfull as a cubscouts eyes.

Hey guys.. sorry for not getting back sooner... as I wrote before I dropped the fork legs, set settings to basic and rode it to no avail... thoroughly pissed off that that didn't help, so I left her in the garage for a few days...
Rode her again a few days later and low and behold the damn thing is a different bike.. handles way better, head shake is almost gone but bearable and clears if I accelerate through it now... back feels lower and softer which I think is helping the issue...
Thanks to everyone who pitched in ideas and information.. it's appreciated

Did you drop them flush with the top triple or below?[/quote]

hey.. I dropped them about an 1/8" below.. all I can think is it took a while for the settings to take effect ie. movement of oil from one chamber to the next... the rear feels alot softer and lower..

I changed the fork oil on my bike recently and found that one of the rebound needles was stuck. I managed to free it up, and with the new oil, the front end stability is much improved. I wonder if you have had a intermittently sticky rebound needle in one or both of the forks?

Any chance the swing arm is loose?