UPDATE:  Problem solved -- it turned out to be the rear tire!  An Avon Storm 3-D XM, it was most likely defective in some way.

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Hey, everyone,

I have been working on a problem with my 2001 Concours for weeks now.  Let me describe what is going on, and what steps I've taken so far to fix it.  I'd like to know if there's anything else I can try before I just throw my hands up and give up here!  This will be a bit of a read, but I'm trying to be thorough and offer as much information as I can.

SOME BACKGROUND
I've owned the bike for a little over 2 years so far.  In that time, it's always been rock-steady on the freeway, up to and over 80 miles per hour.  Recently, the bike sat outside under a CycleShell cover for about 2 1/2 to 3 months, as I didn't have time to ride.  At that time, the tires on the bike were about 6-8 months old, and they were both Avon Storm 3D X-M radials, in the standard sizes for the Concours.  The windshield on the bike is non-stock, and is a Gustaffson 11" shorty shield.  I do not ride with a trunk or with the saddlebags, and have the side-covers installed and the antlers for the bags are currently removed.  The fairing is completely stock, and in excellent shape and has no cracks or other issues that should abnormally affect aerodynamics.

THE ISSUE
I started riding it again at the end of April.  While doing so, I noticed that at highway speeds, there seemed to be a bit of a wobble -- the bike wouldn't track straight, and instead felt like it was... wiggling?  I think that's the best way to describe it.  Below about 70, you wouldn't really feel it beyond sometimes kind of getting a sense of unease.  Above 75-80 miles per hour, it begins to manifest itself as an oscillation of what feels like the entire bike at about 3-4 Hz (so about 3-4 wiggles per second).  In other words, it's a slow wiggle or wobble, not a vibration.

The issue can also be felt at slightly lower speeds by performing very quick maneuvers, such as quickly switching lanes or performing an emergency swerve maneuver, such as you'd use to avoid debris in the road.  At lower speeds, the bike will oscillate and eventually seem to settle down.  At higher speeds, such as around 80 miles per hour, it becomes pretty much constant until you slow down again.

I just want to stress again, this doesn't seem to be a problem that gradually manifested itself -- when I put the bike away at the beginning of the year, I was regularly riding at about 80 miles per hour on the freeway, and it was solid as a rock, with no wavering.

WHAT I'VE DONE SO FAR
I have tried an awful lot of stuff to get rid of this.  Here's the complete listing of the fixes I've had done.  All the work was performed by a competent local shop that specializes in vintage Japanese motorcycles, and they've always done right by me.

New Steering Head Bearings
The first thing I tried was having the steering head bearing replaced.  I've heard that high-speed stability can be an issue with a worn head bearing.  The bike now has a brand-new steering head bearing, OEM Kawasaki, installed professionally.

New Front Springs
The suspension on the bike was worn and quite old, so I had the front springs replaced at the same time with a set of Progressive straight-rate springs (1.1 kg).  This was performed at the same time as the steering head bearing replacement.

New Rear Shock
The rear suspension was also quite old and soggy, so I also had that replaced.  I used a Progressive 465-series shock absorber from Murph's Kits, and again, the installation was handled by a professional mechanic at the same shop.  This was performed at the same time as the two previous fixes.

Front Fairing Repair
While I don't think this will have anything to do with the actual issue, I'm mentioning it for completeness.  My front fairing was cracked and inexpertly repaired by the previous owner right next to both turn signals.  Since the fairing was coming off to do the front-end work, I had the cracks fixed and the fairing re-painted.  I also installed some sick-ass Ninja decals because no one can tell me not to.

Front Fork Brace
As a final capper, I also ordered a fork brace from Murph's, and had that installed at the same time as the front suspension work was done.

After this point, I first got the bike back.  I took it out on the freeway, and noticed that the problem had not been noticeably improved at all, but neither had it been made worse.  Still, given all the work I'd just had done, it was discouraging.  I spoke to my mechanics, who then said that there was some sign of unusual or uneven wear on the front tire.  So...

New Front Tire
Contacting a local motorcycle dealer (as my regular shop is over an hour away from my house), I ordered a brand new Dunlop sport-touring tire and asked that it be mounted, balanced, and installed on the bike.  Took a couple of days to get the tire because of Connie's weird sizes, but they did it without incident.

That was the second time I got it back.  I once again took it out to the freeway, testing for both the wobble at high speed as well as the induced wobble from quick lane changes.  It had not changed in either case, and was still occurring.  So, once more, I called my favorite shop and talked it out with their lead mechanic.  I said that I had read a few articles online, and that one of the other issues that apparently can cause similar symptoms is a missing or broken engine mount bolt.  Apparently, it's not uncommon for these bolts on the ZG1000 to back out, shear, break, or simply vibrate loose over time, and because the engine is a stressed member of the frame, giving it lateral freedom of movement can result in some odd handling effects, including a sort of gyroscopic, side-to-side movement that sounds like it feels something akin to what I am experiencing.

Engine Bolt and Frame Inspection
I returned the bike to my favorite shop, and they spent two days going over it with a fine-toothed comb.  The lead mechanic put a wrench on "every exposed bolt he could find", including the engine mounting bolts, frame connectors, swingarm mounting bolts, suspension mountings, and everything else he could reach, making sure that everything was up to the factory specifications.  They discovered that the two front engine mounting bolts were each about half-a-turn loose, so those were re-tightened.  In addition, they looked over as much of the frame as they could see, searching for any sign of stress fracture or cracking -- peeling paint, rust spots, actual fractures, etc.  They found nothing of the sort.  The only other issue they found was that the right-side footpeg was a little loose, which they also fixed (hey, you never know!).  They test-rode the bike and said from what they could tell, it was improved.

At that point, I reclaimed the bike for the third time, and rode it home.  While it seemed improved and more stable on the road, once we hit the freeway and I was able to get up to 80 again, I was disappointed to discover that the same issues began to appear.  I wrapped it up to about an indicated 90, and the shaking only got worse -- it was visibly moving the handlebars, and my long-suffering girlfriend driving behind me was even able to notice it before I told her about it.

SO WHAT NOW?
So now, here I am, having spent way more than this bike is actually worth to diagnose an issue that remains MADDENINGLY out of reach.  I still want to try to fix it, because at this point, in for a penny, in for a pound, but I'm not sure what else to do here.  About the only thing I can think of that I have left to try is also replacing the rear tire.  Short of that, I honestly don't know what to do here.  I don't understand how this changed so suddenly -- this bike was always absolutely rock-steady in the fast lane for the two years prior to this.  I don't see any missing parts or linkages, all the bearings and fasteners seem to be correct and fitted, there's nothing wrong with the frame...

I would greatly appreciate any words of wisdom that anyone else can offer for this.  I don't want to have to get rid of this bike, I love it dearly, but I mostly ride freeways, and I just don't feel safe riding it with this kind of instability at the kind of speeds that I regularly hit on my commute!

Some folks have had with the Avon Storm 3D X-M radials.
Tires have broken down internally or developed bulges.
Wobble was the result.

I suspect you have a rear tire problem.
I would replace the rear, and probably install a belted tire on the rear.

If you were near me, I'd trade wheels with you to see if it fixes the problem.
Do you live near anyone with a C-10?

Ride safe, Ted

Some folks have had with the Avon Storm 3D X-M radials.
Tires have broken down internally or developed bulges.
Wobble was the result.

I suspect you have a rear tire problem.
I would replace the rear, and probably install a belted tire on the rear.

If you were near me, I'd trade wheels with you to see if it fixes the problem.
Do you live near anyone with a C-10?

Ride safe, Ted

Ted,

Thanks for the reply (I'm watching this thread like a hawk right now).  I don't know of anyone else out my way -- I'm in the Phoenix metro area, and so even if someone was out here, it's 118 degrees today, and I'd hate to swap tires today.  I'd actually just ordered a Mean Streak rear wheel to begin the conversion to a 17" tire in the back, but I haven't wanted to pull the trigger on doing the machine work and getting the tire installed without knowing if I can solve this current problem first -- don't want to throw any more good money after bad, you know?

I think what I'll do is try an OEM Dunlop on the rear, and see if that helps at all.  Do you have any other recommendations other than the OEM rear (...he asked, knowing full well what a can of worms that question might open)?  I figure that might be the safest way to test out whether or not that's the actual problem.  If it works, I can ride for another season or so on the old-fashioned OEM tire (which isn't the best, but is fine for interstate work, commuting, and general around-town work).

Sad to say, my experience with the Avons has not been great, even before this wibbley-wobbley nonsense started happening.  I found them to be a bit too squirrelly for my tastes.  It's a shame, because there just aren't that many nice radial tires for this old girl any more.

There is a discussion about the Shinko Radial on one of the Forums.
They say the Skinko isn't built to hold up the weight of the C-10 and wobbles.
I suspect that may be some of the problem with the Avon Radial.

I was sorta serious about going to a bias ply on the rear. Many are doing this with good luck.
Note, the available (Goldwing size) bias ply tires sets are taller than the radial sizes.
The extra height at the rear will raise the rear a bit and should quicken the steering.
(I think that's why the 55 series is helping us on the C-14's).

NOTE: The bias ply will change the handling of the bike a bit, but the change is manageable.
             Others can chime in about their thoughts on the mixed tires.

Just my 2 cents.

Hope this is helpful.

Ride safe, Ted

I was sorta serious about going to a belted on the rear. many are doing this with good luck.
Also, the available (Goldwing size) belted tires sets taller.
The extra height at the rear will raise the rear a bit and should quicken the steering.
(I think that's why the 55 series is helping us on the C-14's).

Ted,

I guess I'm a bit confused, here.  I thought you meant a steel-belted radial tire, which I assumed the OEM Dunlop K700G was.  Am I mistaken in that regard, or were you talking about some thing else?  Bias-ply, maybe?  I apologize for the confusion.

My apologies. meant to say Bias ply.

NOTE: The bias ply will change the handling of the bike a bit, but the change is manageable.
             Others can chime in about their thoughts on the mixed tires.

Ride safe, Ted

Ensure the steering head bearings are PROPERLY adjusted. Putting bike on c stand and grabbing the wheel and pulling on it wont do it.
They need to be tighter than you think. Tighten them til the bike wont steer properly-it wants to go in one direction and you have to nudge it the other way but it wont go straight-then back off the nut slightly. When it steers properly then the bearings are adjusted properly.

BTW if you have 20k or more on the bike check the front wheel beartings. They come from the EX 500 and arent up to the task of carrying a heavy bike like the Connie especially if you like the twisties.
I went through three sets in less than 50k all replaced under warranty....no, just the first two.

BTW if you have 20k or more on the bike check the front wheel beartings. They come from the EX 500 and arent up to the task of carrying a heavy bike like the Connie especially if you like the twisties.
I went through three sets in less than 50k all replaced under warranty....no, just the first two.

Currently still waiting on the rear tire to come in, but I did make it a point to talk to my mechanic and ask if, during the full-bike inspection I'd asked for, they checked the bearings.  He informed me that they had inspected both front and rear wheel bearings, and everything looked okay there.

Still, if worse comes to worst, it's fairly inexpensive to get the front wheel bearing replaced.  I'd be more keen on doing this stuff myself, but it's over 110 degrees pretty much every day in the desert here, and will be for some time.

Thanks for the advice and suggestions!  I'll check back in on the thread after I've replaced the rear tire.  I am worried that this may not do it, but I don't know what else I can really do at this point.

Although it would surprise me to see it happen suddenly, like after just sitting for a while and then just being there, if your swingarm bearings are not torqued correctly it can cause a wobble, or as it has been described "the ball bearing dance".

If the new rear tire doesn't cure the problem, you might want to ask the shop to actually loosen the swingarm bearing adjustment and torque it back per the manual.

Well, thank you, everyone, for the replies and the advice.  I am happy (actually elated, really) to say that, with a new, stock Dunlop 700G tire, my high-speed wobbles have finally been cured!

I put the bike on the freeway after getting it back from the shop and briefly wrapped it up to [SPEED REDACTED but it rhymes with "fine tea"].  The old girl was as rock-steady as the first day I ever got it, and a couple of quick lane-changes didn't unsettle it at all.

I'm... a little miffed that I spent so much time and effort looking elsewhere before realizing that the rear tire was the culprit, but that's the way these things go sometimes.  I inspected the tire as best I could, and asked the shop doing the installation to do the same, and neither of us could find anything wrong visually.  Anyway, at this point, I've redone the engine top-end, the suspension front and rear, the tires, the fairings, and various other maintenance items.  It's probably about 50% brand new at this point, which I'm hoping means it'll be tires and oil changes for the foreseeable future.

Still, this is something to be aware of.  My regular mechanic is dead-set against Avon tires as a brand, and I admit, my faith is shaken a bit as well.  Best bet is that the rear tire was defective somehow, though in a manner that wasn't readily apparent to the old Mark I Eyeball.  Think I'll stick with Dunlops for the time being.

Thank you all for your advice and well-wishes!

Question is how did it happen from just sitting for 3 months. You had that tire for a while.

Just saw this thread.

Beyond the tires, the C-14 comes with a set of extremely narrow- angle, angle contact bearings in the headstock, which are too light for the bike IMO. Swapping them for tapered roller bearings and then backing off the stem torque value (from ~ 20 ft. lb. to ~ 7 ft. lb.) will dramatically calm the bikes' steering harmonics and any tendency to oscillate at high speed.

I would recommend anyone experiencing any front- end instability or sensitivity on a C-14 to swap the angular contact, stock bearings for a set of quality (not "All Balls") tapered roller bearings installed at a lesser 'set' torque. The difference is 'night and day', and I personally believe Kawasaki had a swing and a miss, not only on the bearing type but the contact angle, which is far too shallow for the bikes' weight.

Some have said that tapered roller bearings will slow down the sensitivity of the steering, and those people are sorta' right, although a 700 lb. bike never could have much steering sensitivity in the first place. It is not noticeable in actual riding but it does wonders for overall bike stability and removes the need to tighten the steering head bearings every ten minutes or every 150 miles, whichever comes first. 

Brian

Well, thank you, everyone, for the replies and the advice.  I am happy (actually elated, really) to say that, with a new, stock Dunlop 700G tire, my high-speed wobbles have finally been cured!

I put the bike on the freeway after getting it back from the shop and briefly wrapped it up to [SPEED REDACTED but it rhymes with "fine tea"].  The old girl was as rock-steady as the first day I ever got it, and a couple of quick lane-changes didn't unsettle it at all.

I'm... a little miffed that I spent so much time and effort looking elsewhere before realizing that the rear tire was the culprit, but that's the way these things go sometimes.  I inspected the tire as best I could, and asked the shop doing the installation to do the same, and neither of us could find anything wrong visually.  Anyway, at this point, I've redone the engine top-end, the suspension front and rear, the tires, the fairings, and various other maintenance items.  It's probably about 50% brand new at this point, which I'm hoping means it'll be tires and oil changes for the foreseeable future.

Still, this is something to be aware of.  My regular mechanic is dead-set against Avon tires as a brand, and I admit, my faith is shaken a bit as well.  Best bet is that the rear tire was defective somehow, though in a manner that wasn't readily apparent to the old Mark I Eyeball.  Think I'll stick with Dunlops for the time being.

Thank you all for your advice and well-wishes!

Question is how did it happen from just sitting for 3 months. You had that tire for a while.

My guess -- and this is really coming directly from my nether regions here -- is accelerated break-down due to the wave of heat we've had, but at this point, your guess is as good as mine.  It may have been just an irregularity or defect in the tire's construction that eventually gave way, and all of my riding back and forth to the shop to "fix" the problem was only exacerbating it.

Sounds like great news Rob.
Glad you finally found the problem.
I see you went back to the stock tire on the rear.
Wish there were other radial choices.
Are you planning a trip?

BDF: Rob's bike is a C-10.
        But, this is the first I've read about the C-14 having a front end problem, and that it does not have TRB's..
         Sounds like a good fix.
        What (Tapered Roller bearings) and races would you order to install in the bike?
         Would C-10 bearings/races work?

Ride safe, Ted

Whoops- my mistake, I did not even realize I was in the C-10 forum.

I am apparently a little unusual in that I have never owned, worked on, ridden or gained much of any knowledge about C-10's. I was introduced to the Concours starting with the 08, 1400 model and so do not know anything about what swaps, what is like it was on the C-10 and so forth. I claim complete ignorance :-)

Not sure what size T.R.B. fits the C-14 but it is a standard industry size, readily available at any bearing house. I am using a set of the brand 'All Balls' but do not recommend them as they are of poor quality although for this application, they do seem to work fine. What I would do would be to take out the stock bearings, measure them and then grab some from a local bearing supplier such as Kaman, or even a reputable place on-line.

Sorry for jumping into this thread by accident, and none of my information applies to a C-10 as far as I know.

Brian

Sounds like great news Rob.
Glad you finally found the problem.
I see you went back to the stock tire on the rear.
Wish there were other radial choices.
Are you planning a trip?

BDF: Rob's bike is a C-10.
        But, this is the first I've read about the C-14 having a front end problem, and that it does not have TRB's..
         Sounds like a good fix.
        What (Tapered Roller bearings) and races would you order to install in the bike?
         Would C-10 bearings/races work?

Ride safe, Ted

https://youtu.be/uNwQK_HIHRU

i hope that nothing ever ends like this for anyone else.

Sounds like great news Rob.
Glad you finally found the problem.
I see you went back to the stock tire on the rear.
Wish there were other radial choices.
Are you planning a trip?

BDF: Rob's bike is a C-10.
        But, this is the first I've read about the C-14 having a front end problem, and that it does not have TRB's..
         Sounds like a good fix.
        What (Tapered Roller bearings) and races would you order to install in the bike?
         Would C-10 bearings/races work?

Ride safe, Ted

No trips in the near future, but my daily commute is about 45 miles one-way, almost all freeway, so I need my girl to be at her best at those speeds.

The stock Dunlop is okay, not super-great, but good for packing on the miles.  However, I have a 17" rear wheel from a Vulcan Mean Streak that I will be having machined to fit the Concours rear end later this summer, after I have gotten some use out of my new K700G.  That should significantly improve my available tire selection.

I am just over the moon that my bike is stable again.  I very, very nearly swapped her for a 40,000-mile ZZR1200, but I think I'm actually glad I stuck with Connie in the end.  I don't need the top-end on the ZZR, and Connie carries more stuff.

Whoops- my mistake, I did not even realize I was in the C-10 forum.

I am apparently a little unusual in that I have never owned, worked on, ridden or gained much of any knowledge about C-10's. I was introduced to the Concours starting with the 08, 1400 model and so do not know anything about what swaps, what is like it was on the C-10 and so forth. I claim complete ignorance :-)

Not sure what size T.R.B. fits the C-14 but it is a standard industry size, readily available at any bearing house. I am using a set of the brand 'All Balls' but do not recommend them as they are of poor quality although for this application, they do seem to work fine. What I would do would be to take out the stock bearings, measure them and then grab some from a local bearing supplier such as Kaman, or even a reputable place on-line.

Sorry for jumping into this thread by accident, and none of my information applies to a C-10 as far as I know.

Brian

 

As a side note, the only wobble (decel) I ever had with my C10 was due to the front tire.  Went away after I eventually changed it out.