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Old 01-30-2013, 07:57 AM   #1
Edder B OP
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Head Shake

Went out riding yesterday. 65 degrees in January, what a great day. Anyway, as I was slowing for a light going around 60 mph I let go of my handle bars and started to get a head shake or slight tank slapper. Tried it again at a lower speed and it did it again. Never noticed it before and I'm wondering if that's normal for the KTM and if not, what would cause it.
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Old 01-30-2013, 08:18 AM   #2
mcmann
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Scoot up on the seat and try it . . . . Need some weight up front. Some tires cause head shake on different bikes. Sometimes, raising the forks in the triple clamps will help . . . Puts a little more weight on the front tire. Sometimes, you can rotate the tire on the rim and it may help.

I had a MT90A front tire that was fine until I swapped it back and forth with a more aggressive tire (TKC80). I developed a slight hands off head shake that I could not get rid of (re-balanced & rotated) . . . Finally, put the TKC80 back on which was fine. The next MT90A had no head-shake????

Tires and head-shake can be a mistery
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Old 01-30-2013, 08:39 AM   #3
geometrician
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Eek Deceleration Wobble

"decel wobble" is what you're experiencing , as opposed to "accel wobble" where the front end goes light under accleration and the tire skips over imperfections in the pavement. Yes, it is common on the Adv's as well as many other motorcycles.

Among possible causes are: steering geometry; suspension settings; tire design; tire inflation; tire wear; distribution of rider/passenger/gear.

Generally speaking the more quick-steering & "nimble" a bike is the more likely decel wobbles occurs as more weight is shifted to the front end.

One solution is to fit a steering damper, which damps (slows) the oscillations down before peak energies begin to move the front end from side-to-side, which can increase to what is commonly called a "tank-slapper" where the front end goes from full-lock to full-lock. This wave amplification can build quickly on some bikes to the point of the handlebars being torn from your hands which generally ends in a crash. Steering dampers are included on many newer motorcycles (usually sportbikes) and help greatly when riding offroad to prevent the front end from being deflected by rocks, bumps, ruts, etc. Great investment! Personally I am a fan of the Scotts damper though there are several to choose from.

Here's an example from the Isle Of Man TT races
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Old 01-30-2013, 08:39 AM   #4
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Suspension setup and tire wear are the usual suspects. The stock scorpions are known offenders. What changes did you make before you noticed the shake? You said you were decelerating which loads the front so adding more weight there is probably not the answer. Did you remove luggage and not adjust the preload?
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Old 01-30-2013, 08:51 AM   #5
BoulderGuy
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Stock front tire?

Mine did the same thing with the stock Pirelli front tire. (but has never done it with any other tire) Go figure...
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Old 01-30-2013, 08:55 AM   #6
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Quote:
Originally Posted by mcmann View Post
Scoot up on the seat and try it . . . . Need some weight up front. Some tires cause head shake on different bikes. Sometimes, raising the forks in the triple clamps will help . . . Puts a little more weight on the front tire.
Raising the forks tubes in the triples reduces trail & makes the bike MORE sensitive. Trail give self-correcting steering; ie the less trail you have the more chance of the bike shaking the front end.

You want less weight not more!

Oh yeah the front Scorpion is bad even when new!
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Old 01-30-2013, 08:59 AM   #7
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One simple solution is to tighten up the steering head bearings. My '05.5 950, with 90,000 miles, never had head shake while my '12 990, with 11,000 miles, had decel headshake until the bearings were tightened. Now there is no problem.
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Old 01-30-2013, 11:41 AM   #8
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The tyres are the usual thing, and as said Scores can do this even when new! Suspension set up goes a long way, with tons of theories, but I personally found it cured as a side result of putting 0.64 springs in.
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Old 01-30-2013, 12:25 PM   #9
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as others have stated tires and or wheel balance is an obvious place to look
also
don't overlook the rear wheel alignment i.e. make sure it is on track with the front wheel
if it's out enough it will steer the bike one way while the front wants to go the other setting up an osculation
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Old 01-30-2013, 12:37 PM   #10
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Thanks for all the responses. I did recently put new set of Heidenau Scouts on but I think I need to check the head bearings.
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Old 01-30-2013, 03:16 PM   #11
marin ktm
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Quote:
Originally Posted by BoulderGuy View Post
Mine did the same thing with the stock Pirelli front tire. (but has never done it with any other tire) Go figure...
Me to. I have had 3 Pirelli Scorpions and every one wobbled. I don't buy them any more.
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Old 01-30-2013, 04:15 PM   #12
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I've run Scorps in the front and didn't have any head shake. Though the few times I did have head shake my preload wasn't set right.
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Old 01-30-2013, 04:20 PM   #13
DirtyADV
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Scorpion Tire Shake! All I have had have started shaking after some wear:



Not that badly in this movie have seen worse on previous tires.

/Johan
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Old 01-30-2013, 04:46 PM   #14
Katoom72
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Quote:
Originally Posted by DirtyADV View Post

Not that badly in this movie have seen worse on previous tires.

/Johan
Exactly what my adv did on stock tires. The Hidenau's go in a perfect straight line.
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Old 01-30-2013, 05:19 PM   #15
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Quote:
Originally Posted by DirtyADV View Post
Scorpion Tire Shake! All I have had have started shaking after some wear:



Not that badly in this movie have seen worse on previous tires.

/Johan
Not bad at all, I have plenty of bikes that were way worse, road surface the amount of weight transfer on decel, all play a part as well..
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