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i recently got an 06 yz250f and its been great so far. but some of the time when i land my bars start swapping back and forth. it also happens on braking bumps but not that much. is it rider or bike? im landing with the throttle on and im squeezing with my legs when braking. i checked and my wheel is aligned with the bars. would stiff suspension have anything to do with it? im 115lbs and i have stock springs. i have the comp damping as soft as it can go, and the rebound 4-6 clicks IN. im hitting decent sized jumps -50-120ft alot with braking bumps right after the landing

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Im not to much bigger than you and am having the same problems.

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I was playing with my fork height some time ago. I raised them to 15mm above the clamps. Head-shake was horrible. So the are now back down to 2 or 3mm.

I would check that.

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The reason you get it is because the springs are too stiff for you and the valving is off for your weight. Have it resprung at the minimum and re valved if the problem is still occurring. But as for getting headshake on braking bumps try grabbing your front brake harder and it should stop the headshake. as far as rider technique goes as long as your wide open and leaning back a bit you shouldn't be getting headshake ( I realize this isn't possible for everyone) I get a little bit of headshake when practicing but when racing i don't get any at all because i'm either wide open or on the brakes.

I weight 110 pounds with correct springs and rear shock re valved, (front will be done soon)

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thanks for the advice st3vo. im WAO and leaning back when it happens the msot actually. your right about not using enough front brake though! i wasnt using it as much as i should cuz the bumps are way harsher and whoop my ass when im hard on the front brake. if i get new front springs would i have to get a new rear spring too? i dont wanna throw the balance of the bike off with really soft springs in front and stiff stockers in the rear. i dont think i can afford both front and back =/

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If you were to get new springs I would definately suggest you get front and back. Also its not just the front that you need to worry about with headshake the back also has a major contribution to it. If the rear spring is too stiff it will not absorb the bumps like the correct spring would and it will kick a little bit causing the weight to be transfered to the forks (however I'm no expert)

IMO either get both front and rear springs or just put up with it, hard rear and soft front will have a negative effect on the bikes handling.

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id go with lowering the forks in the clamps first like tha breeze said, i had that problem and worked a treat, there now just above flush with the top of the fork and the top clamp and its unlikely, but you might have the pressure on your headset bearings too loose.

hope that helps

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HI,

Is your sag set correctly? Not enough sag would be one reason the front is shaking; the back is too high and the front end geometry too steep.

Another reason may be your weight, or lack thereof. The spring rates are too heavy, and you are not able to get into the "meat" of the travel. You're just skimming the initial few inches. Then your bike is rebounding too fast thus causing the skittering.

Or your rebound is set too slow and the suspension is packing on the small stuff thus causing the shaking and chattering.

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I'm lighter same bike but 07' when we got it I got alot of head shake just even in 2gear so we redid the springs and all they werent set right still but i got into mid 3-4 and I would get head shake, we just chnged my back spring to make it even softer that helped, havn't noticed any at all yet, and we are changing the little springs in the forks and thats is supposed to save it...

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Many times, headshake is a result from poor bike set up and/or riding technique. I would go to a suspension service shop and get your bike set up for your weight and speed.

Another tip is to limit chopping the throttle and instantly putting excessive weight onto the front tire

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The main reason you get head shake is because the front end is too low in relation to the rear end. Check the rear shock spring's "Rider Sag". It should be between 105 and 110 mm.  If the measurement is lower, you have too much p reload on the spring.  This will make the front end too low.  Or you're rear shock spring's preload maybe okay, but your front fork springs maybe too soft or not have enough preload.  Another way to fix this head shake problem is to drop the forks in the triple clamps.  3mm will make a noticeable difference.  

There's always a happy medium with chassis and suspension setup.  You have to try one adjustment at a time until you like it. 

You maybe interested in my Bike Set Up DVD.

 

SZ_VO1_DVD8_back_cover.jpg

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