I was cruising at 75 MPH over semi-crappy pavement, throttle lock engaged, and she went into a violent head shake - nearly lock to lock. Was able to come to a stop and point toward home - made it uneventfully.

Tires were inflated pretty high - probably a pound over the 42 the manual suggests. The PR4s are worn out - just at the wear bars. I've got replacement Michelin PR4s already ordered - I'm thinking that should cure it. What else should I have my mechanic look at? Never had any head shake previously and I'm at 11,400 miles.

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I did my fastest run ever on Pirelli superbike pro slicks. The front was almost shot and the rear was to where you could see the ripple wavy texture of the carcass about ready to show through. No problems. 180 mph. I do have a steering damper. It seems hard to believe a worn tire would cause this but unless you have the rear lifted a/o the front lowered, that would be my only guess. The 14's rake is pretty low compared to most sport bikes.

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The suspension setup is stock. Looking at the tire, the left side is more worn than the right. I don't get a lot of lean angel wear so I'm not sure what caused that. I think I'm going to have them take all the weights off the wheel and rebalance from scratch when the new tires are mounted. Is this a good idea?

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Worn tires will definitely cause head shake...Never heard of it being so extreme tho.. It has been my experience that it is usually first noticed at low speeds...

Worn tires will definitely cause head shake...Never heard of it being so extreme tho.. It has been my experience that it is usually first noticed at low speeds...
Suedez. you say you had the throttle lock engaged.. were you still holding the bars are holding them very lightly?

I think I'm going to have them take all the weights off the wheel and rebalance from scratch when the new tires are mounted. Is this a good idea?

I have heard of track riders making no attempt to balance other than throwing some dyna beads in the tire. I have personally found my stick on weights missing. Your tire surely does not stay in balance as it wears....nobody takes it off to have it rebalanced. MC tires are tons more forgiving than car tires, especially wide car tires. I do not think dynamic balancing makes a lick of dif on a bike. NO balancing does not seem to make a lot of dif. SO in a word, NO. NOt exactly a bad idea but probaly not a good one. Then again, Im not the guy who experienced the tank slapper. IDT you want to test out different things by trying to duplicate this same situation.

Having a lot more tire wear on one side is unusual especially if you have no explanation. Seem to recall someone else saying they had a similar problem recently and it was corrected by a new tire. Something in my memory bank is telling me to tell you to look for cupping. It might be very subtle but do you see or feel a scalloped surface on the tire? I think that was aforementioned guys problem and he was actually able to show it in a photo so he at least was able to see it...though you may only feel it.

I do not think it was over inflation either. I run 45 lbs f/r when I do a road trip. Never a problem.

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well---when you get a new tire, yes might as well balance.

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shouldn't asymetrical wear be normal on old tires, up to a certain extent?
tires sides run different distances, whether we take a left turn or a right turn

this difference, even though it is small, will add up with increasing mileage
it seems to be more obvious on the front tire

Tires will wear more on the left side due to the crowning of the road.

I'd check everything.

New set of tires (stock size - rated for bike "E" rated or what ever)

Balance tires

Make sure when reinstalling front tire that forks
are settled correctly.

"Align" tires

Get front end off ground check for play in stem bearings.

Have you serviced front forks since new (2012)?

Is the suspension set up correctly?

Have you done anything like raised the rear or dropped the font?
If so change it back.

Any kind of luggage on bike? Just asking.

* Last updated by: piken on 1/29/2017 @ 7:51 PM *

Everything is stock, no luggage and I haven't serviced the forks yet. They feel about like new though (until today!).

I was holding the bars lightly with just my right hand.

How do I make sure when reinstalling the front tire that the forks are settled correctly?

* Last updated by: suedez on 1/29/2017 @ 8:10 PM *

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Before tightening the axle clamp bolts, you want to pump the front end up n down 4 or 5 times with the front wheel chocked, not using the front brake. Then tighten the right fork first, then the left...15 ft-lb.

* Last updated by: mad5674 on 1/29/2017 @ 8:26 PM *

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The pumping and axle clamp bolt tightening is after tightening the axle nut to 94 ft-lb.

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"Everything is stock, no luggage and I haven't serviced the forks yet. They feel about like new though (until today!).
I was holding the bars lightly with just my right hand.
How do I make sure when reinstalling the front tire that the forks are settled correctly?"

My bet is on worn tires.. On certain brands it is very pronounced..and if the ONLY thing having changed in the last couple of thousand miles is teh wear on the tires..I will betcha lunch at a drive up, that that is/was teh problem...

* Last updated by: chrly on 1/29/2017 @ 11:00 PM *

G'Day suedez,I am not nearly as apt as some of the experienced guys here and unfortunately don't have the easy answer for you, but getting head shake on a super stable bike such as the ZX-14R would really ring alarm bells to me. I have been up to some substantial speeds on my 14 and it has never been anything but planted. Something is surely amiss so take it very seriously regarding finding the issue.
Perhaps you might also consider a top quality steering damper as insurance?
A lot of guys say they are not needed on the 14, and they are probably correct the majority of the time.
But then something like your situation comes along...

To Steeping Damper or Not

* Last updated by: yannih on 1/30/2017 @ 4:09 AM *

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"semi crappy road surface"...HOW semi crappy?"Worn tire"(hardened rubber,overinflated)...=slip..even a minor slip under the right circumstances.Tire hits a hole(or groove)...tire gets momentarily off alignment...power still on,sounds like that to me.It only takes a second,as you know...no warning.The MFG says...'on rough roads,grip the tank with knees,and SLOW DOWN".
I'm really glad you stayed with it.Had that happen to me on my zx12R...in front of a semi.scarey.One more whip either way and I'd have lost it for sure.Only thing(I think)saved me was my hands got torn from the bars,so the throttle closed immediately.Mine did go from stop to stop about 5-6 times.

I didn't end my ride,but it wasn't that 'fun' after that.Remember it clearly to this day.

* Last updated by: Grn14 on 1/30/2017 @ 9:37 AM *

Had a bad tank slapper at about 130 mph under full throttle. I went home and ordered a Scott's steering stabilizer and so far no problem.

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The road was U.S 90 West just outside of Del Rio, Tx. There weren't any potholes, just uneven pavement from years of big trucks and massive Texas heat cycles. I retraced my path and evaluated the pavement where it happened, slower and with two hands to see if I could replicate the headshake - didn't happen. Nothing felt normal though - perhaps from the tires/ road conditions and partly from my moderate case of the willies from the headshake incident.

This bike has always been extremely planted - never any headshake like my CBR954RR did under hard acceleration when the front end was unloaded and I hit a small bump. I'm not planning on buying a steering damper - got a kid to put through school and I am certain something is simply amiss - probably just a combination of being too much of cheap bastard and riding the front tire a little too long coupled with lazy riding technique of one hand coupled with shitty pavement (which is everywhere and we just have to deal with it).

I'm going to be extra careful though to thoroughly rag on my bike shop to make sure the new tires are carefully balanced and all the great gouge you guys have provided is adhered to when putting the front end back together. I am very jealous of you competent wrenches out there who don't have trust a bike shop mechanic.

You guys and your collective experience and wisdom rocks!!- thanks!!!

* Last updated by: suedez on 1/30/2017 @ 6:03 PM *

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Most likely a combination of the road surface, worn tires, and one hand on the bars.

What we're really talking about is an oscilation and magnitude. All of us have headshake, all the time. It's at a magnitude that is imperceptable. Think of it as around the world 1.0 magnitude earthquake happen hundreds of times a day around the world. But we only notice them if they're substantial.

My take on headshake like you experienced is a result of harmonic coupling. Different parts of your bike are vibrating at different rates. Occasionally these harmonics couple (say one part is vibrating at 30 hz, and one at 60hz), which results in amplification of energy as the two signals sync up together. Most likely, your tires started vibrating due to their wear and the road surface, this coupled with whatever other frequencies were running through your bike at the time and you got slapped around a bit.

Glad your ok headshake like that has to be quite an experience, at least requiring a change of underwear.

I think I might not do any more high speed runs with worn tires.

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The harmonic coupling sounds like the likely culprit - great explanation. I'm definitely going to replace the tires a little sooner next time - not just rely on the wear bars for replacement guidance. Thanks.

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Have you serviced front forks since new (2012)?

What exactly does this service consist of? Thanks...

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I'm gonna guess on the headshake deal...probably rock hard front tire.Not allowing it to flex like it should over bumps and such.Rock hard meaning...at the end of it's service life.Heat cycles.It has to absorb SOME of the road surface,if it can't,it'll skip(side to side)...though you may not feel it...until...once she's out of rear end alignment,there ya go...a setup for a slapper.

Headshake is typically from: Too tight on the bars. I'd wager you got *really* tight on them when it started to shake...

What got it there, in the first place? Dunno. My headshake adventures with the 14R always seem to begin with: too tight on the bars.

I can usually induce a bit of shake by holding tight, and transitioning across two freeway lanes, with the lanes having a bit of "cant", or slope between them, at the dividing line. Like this: Hold tight, and change lanes. Feel the bump going over the cant between the lanes, and then feel the slight headshake.

I have a spot on my commute that I can feel this most every time.

Your takeaway is: Too Tight on the Bars.

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The front tire was hard and I did progress to a death grip on the bars in an attempt to dampen the headshake.

Had the new Michelin Road Pilot 4s installed and balanced, the steering head and alignment checked fine. Was out gradually expanding the envelope and she was running like new. Then all hell broke loose - sounded like the top of the motor fragged itself somewhere.

Shut down and got roadside assistance. Since it was Sunday couldn't take it to the shop - I'm going to get it there in the next day or two. Luckily, I'm hoping, it looks like I still have a couple months left in the 48 month extended warranty I purchased. Sounded nasty / expensive. I'm on a freakin roll.

I'll let you guys know what happened when the shop figures it out.

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What exactly does this service consist of? Thanks...

Oil Change.

Lots of people never change their fork oil. Bike can be several years old and still
has factory oil. It's dirty, thin as water and lubricity has broken down.

I like to change mine every 12 months following what most suspension guys
will recommend.