Dumbfounded with headshake problem

First off, I apologize for the length of this post, but my mechanic and I are dumfounded by this headshake problem so I want to post as much info as possible. So here goes;

bike: 2006 Vtec no ABS bought new in 2007 in the US, moved to Spain late 2010

problem: head shake on deceleration, with hands off the bars, around 160 Kmh and from 90-75 kmh (I know you're not supposed to ride hands off, but we all do it some time and the bike NEVER did this before) from what everyone says and from my own experience this is one of the most stable bikes built.

done so far: new tires, rebuilt forks, checked spring length for damage during shipping to Spain and everything is OK, checked and repacked steering head bearings, replaced wheel bearings.

result: deceleration headshake at 160 kmh is gone and headshake is down to a couple back and forths between 84-79 kmh barely perceptible with a light touch on the bars.

I believe my mechanic has taken this on as a personal challenge and I'm wondering if I should just live with the result. But, it bothers me too. He is going to try adjusting the front left caliper where it combines with the rear and see if that eliminates the last bit of headshake. Anyone experience this also? Any ideas would be appreciated. Thanks in advance

 

try repaving the road or invest in a steering damper.

 

A VFR should not head shake, the only time I thought my VFR was a little nervous at higher speeds was on the triangle profiled pilot powers when I'd dropped the forks to 15mm after fork oil change through the triple clamps to quicken Turn in, raising back to 8mm cured it.

As for coasting down with no hands on bars don't think I've ever tried it so don't know about your slow speed issue.

 

Sounds like you have already hit the usual suspects, that being the head bearings and the wheel bearings. I would be looking at the front tire wear and trying different pressures to see if it helps. Changing the stock head bearings (balls) to tapered rollers makes a huge difference as well.

 

I've already considered a dampner, but that would mask the problem. It never happened before and I would like to know what is causing this.

 

I agree, you've hit all the obvious causes already. During the fork rebuild were the tubes checked for straightness?
When you say you changed the wheel bearings, did you mean front only? I ask because it is possible that a bad rear bearing could possibly contribute to this condition. The cause may not be limited to the front. The rear shock and swingarm pivot bearing are other areas I would have checked out.
When you picked the bike up after shipping, did it appear that any damage could have happened? Was the bike excessively compressed down on the suspension while shipped?

Other than that, if you want to keep chasing it, you could have the frame (and forks/swingarm) checked for straightness at a shop like GMD Computrack (or the Euro equivalent).

In my experience, tires are the most common contributor to this condition, and on VFRs in particular I have felt this before replacing the front tire. I notice that VFRs seem to wear the front tires differently than other bikes I've had, they seem to develop much more cupping on the edges of the rain grooves. The last time I replaced the tire, I looked for a good tire with rain grooves that are oriented more circumferentially than across to help minimize this, and my results have been great.

I feel for you, having a nagging problem that you just can't seem to nail down. I hope you can restore your bike to perfect again.

 

Front tire, even new some brands will cause a little head shake.
My Metzler M-1's shook ( only hands off bars ) and my M-3's do not.
To be honest with you, it is not an issue and you shouldn't worry about it.
It has something to do w/ the tire tread pattern and the newer profiles.

 

My mechanical ability is next to nothing, so I always start with the easiest stuff. I've had the head shake problem as well, and even the lightest touch (i.e. a single finger) on the bars, and the problem would go away.

A couple mentions of tires were made, and that's where I'd be focusing. But I'm not sure if you're saying the tires were mounted in the USA and you had no problem, and then the problem started after the shipping. Or did you put tires on over there and it started?

If the tires were done before your move, did the bike sit for a while during shipment where maybe you have a slight flat spot (not even visible to the eye, but certainly would have an affect at speed).

It sounds like your mechanic has been thorough, and I'm sure you've dropped few $ there. Any way of getting them to mount and let you try a new tire (before actually purchasing)? If the problem goes away, buy the tire (or tires).

For what its worth, tires cured my head shake.

 

I will admit that this happened on my last bike. I hit a huge crater - er chunk of the road was cut out and no signs were placed. I hit it pretty hard. I was looking at the rims being perfect again, the head, triple tree, bearing, brake rotors, forks, fork springs, lower fork seals, and even with a steering dampner it would still twitch bad on a hard brake situation. I took it to two different mechanics, many different times, one very meticulous and the other one even more so. I could never get it right again. I eventually gave up, got my VFR. But I still miss that bike, and knowing that it got the best of me makes it that much worse. I figured that between not being able to ride time and money spent, it was best to cut my losses.

 

You might have some luck replacing the steering head bearing instead of repacking it. Some VFRs had bearings with plastic races.. Not a good thing.

 

Badbilly, good advice.
It has been my experience that torquing the steering head bearings to specs doesn't always work.
I like to put the bike on it's center stand (on my motorcycle lift) and strap the back end down so that the front end is free to rotate left and right.
Then I torque the steering head bolt to the specs and then rotate the front and tighten more until there is a slight drag.
Take it for a test ride up to around 60mph and take both hands off the handlebars and see if it does a head shake.
If yes, back to the garage for another tightning until the head shake is eliminated.

 

A buddy of mine had a similar problem with a high speed headshake on his Kawi Ninja 750. He initially brought the bike over to my garage complaining of looseness in the front end. An inspection revealed that his fork bushings were badly worn and his head bearings were toast. His front wheel bearings had a "gravelly" feel to them as well.

We replaced the steering head bearings,wheel bearings,and rebuilt his forks. When we were through doing that my buddy took his rims and polished them. When he was done with that I installed the wheels and took the bike out for a test ride where I discovered that when I relaxed my grip on the bars it now had a fairly good headshake at high speed.

I removed the front wheel,unbolted the rotors and discovered that when my buddy bolted the rotors back onto the rim he somehow got a big honkin' dollop of polishing compound trapped between the right side brake rotor and the rim. I cleaned that out and retested the bike. Much better but it still had a tiny bit of a headshake at high speed which got worse when you used the front brakes.

I got out the dial micrometer and checked the runout on those front brake rotors and sure enough the left side rotor was out of spec. A closer inspection of that rotor revealed some damage. It looked to me as though the front wheel might have been leaning up against something and had fallen over and the rotor had hit the ground hard enough to cause that damage. My buddy swears up and down that never happened but the evidence on the rotor said otherwise.

We picked up a good used rotor off Ebay from a salvage yard and installed it,then took the bike out for another test ride. Problem solved.

Dunno if that's what's causing your headshake Cecilio,but since you checked everything else of note it couldn't hurt to have your mechanic check the runout on your front brake rotors too. It's possible they might have been damaged when you had your bike shipped.

 

FWIW I had headshake problems and changing the head bearing cleared it right up. Obviously you've tried that though

Hope you get it figured out!

 

If that doesn't correct it. Then take a look at the rear wheel/suspension. Some problems there will show up as head shake also.

 

One thing have u mounted anything on the bars or dash? Like GPS mounting? If its off centre it could cause some headshaking....but I suspect its because during shipping they tied down the bike a bit too hard....check the fork springs and your rear shock it could be the cause....maybe can strip both forks and rear shocks and rebuild them again.

 

The whole front end of the bike rides on the steering head bearing. If and correct, I am reading this wrong, the extant bearing was repacked not replaced. Plastic races? That part is still up in the air.



I do agree that mounting one of the 700lb early GPS units (vacuum tubes) off center could be a problem.

 

i was going to suggest looking at the arse end, could be almost anything, any vibrations tend to work them selves to the head like that, chain sprockets, cushdrives even...

 

Headshake

Others have posted some good things for you to consider but I will add my two cents worth.

Several years ago I had an ST1300 that had up-graded suspension, very carefully adjusted for my weight and riding style. I put a new front tire on (a Dunlop d204) and it immediately developed a head shake on deceleration at about forty mph. Replacing the tire with a different one ( I went to a different brand altogether) fixed the issue.

I am not saying this is always the problem, just that it was for me in this instance.

My current 06 VFR (30k miles) tracks smooth.

 

+1. Perhaps you replaced a not-ideal tire with another not-ideal tire, thereby not eliminating the shakes?