Greetings all,

I have a 1985 RS, my girlfriend has an '84 RS. Mine has a mild occasional steering wobble, hers has just developed a wobble severe enough to worry her and not ride it until fixed.

Some tedious googling revealed that people say "wobble" or "headshake" (or "head shake" or "head-shake") and these are the proposed solutions:

1. Steering head bearings loose/stuffed (oddly enough...)
2. Rear shock loose/stuffed
3. Front forks loose/stuffed
4. Either wheel out of true/round
5. Either tyre worn/flat, or just a brand characteristic (I have Bridgestone BT45s, she had Metzelers)

Has anyone else encountered this problem with a different cause? And are there any other symptoms we should look for which could help narrow down to a solution?

Much obliged,
Jonathan

Yep, mine does it. 60 kph, off throttle, loosen the grip on the bars...and boy, does it shake! If I took my hands right off the bars, it'd spit me onto the road in a flash.

My R100S did it, my R80 RT did it, but nothin' like my RS. I'm having a look at my steering head bearings soon.

Forgot to add...my PO had Metzelers and I now have BT45's.

I also know someone who had one new, and sold it after a nasty shake with luggage and wife on board. And on the other hand, we keep running into people who say "I had one of those - I did about 400,000km on it." One of them now has a Honda ST1300, which is a downgrade if ever I saw one.

I have seen a vague reference to some wheels being made with a not-quite-perfect axle alignment, but this is an onset, which means change, so I doubt that one.

J

Who fitted the tyres?
Tyres are marked with a rotation arrow and a spot circle. The spot should be set next to the valve to give the manufacturers balance and in normal riding I found this to be sufficient Balancing. I am a tourer and not a racer so the extra balancing is advised when very high speeds are used.
I have Avon as my first choice. ( Only on one bike) the rest all different and I have not experienced high speed wobble.
Head bearings are more noticeable on slow cornering.
As a thought , have you checked the oil level in the forks?
Ajays.

My K-RS occasionally gave me a fright, exiting corners at decreasing speeds only, with slight ripples in the road surface. The headshake was so bad I thought I was being talked to by a higher power...I took off the worn Bridgestone S11s (an ordinary tyre if ever there was one) and whacked on a set of Pirelli Sport Demons, and did nothing else. Now I am left to decide whether it's a 'higher' power talking to me. But the headshake's not returned.

I personally know few riders using a Canadian product call Dynabeads. They are 100% satisfied by this product and will never go back to weights. The next time that I will replace my front tire, I will try it too.
Last week, a friend just installed a new tire on her K75 and she was planning an 800-1000km ride for the week end. This is the first time that she uses the beads, and I will ask her if she found a difference.

Dyna beads are high-density ceramic beads that continuously balances the tires as you ride. The amount of material will distribute itself in weight and position dependent on the balance requirements of the individual tire.

You will need 2 oz of beads per tire. The cost for balancing 2 tires is $18.95

Check their Web site here

Hi Jonathon,
Have not checked if the RS has the same geometry as the RT but I have never ridden a bike with a more secure feel.
I am only running fairly ordinary Macadems but have stuck to the recommended size. I am not that fussy about tyre pressures either.
The worst I have felt is a "squirm" under unusual road surfaces but I have also been able to ride the bike albeit slowly with a flat front tyre for about 30k's

Ultimately I would be going through all the ideas you have including swing arm and wheel bearings and maybe even trying some higher bars as they will give you much more leverage.
One thing I did have although with no warning was a broken handlebar mount so definitely worth checking.

I think it's time to do a quick summary:

This appears to be a common issue (there may be a factor of these bikes being so precisely engineered that they're susceptible to minor problems, for all I know...), as I saw elsewhere.

Could be broken handlebar mount. Suppose so, worth checking.

Popular money is on tyres - both our tyre sets were new when bought - both had to be, to pass roadworthy - and I'm getting a new set in two days time. I have only randomly felt this, and more when the bike was new, so maybe something was settling in. Will be interesting to see what happens after my tyre person - who is fantastic - has put new rubber on.

My gf hasn't put many miles on her bike, so tyres still good, and it came on suddenly. Was fine earlier in the day on a quick highway run. Weight coming off rim, perhaps - unbalance?

Haven't ever checked fork oil in either bike or known when it was done - could be worth a look, I've already got the washers etc. to do a proper change for both bikes.

I've gone around her bike on the centrestand and pulled, twisted, wobbled and violently yanked everything with no sign of movement that doesn't seem normal and just like my bike, including the bars, and the tyres are perfectly seated at each end.

Oh, and - nothing wrong with her tyre pressures, or mine. In fact I know I've dipped 4psi in either end on a couple of times (800km weeks and always in a sleep-deprived hurry, was what that was) and haven't noticed any wobbles, just a sluggish touch in corners.

I'm going to ask to take hers for a run and see how it compares to mine, as a first step. And yes, I'll be careful.

I agree with Phil that it's incredibly secure (also a great bike for Tasmanian winters, particularly as RT) - the first decent run we went on together, we came to the top of a set of twisties and my gf described it as a cross between a Katana and a Moto Guzzi Sport. I'm still envious she got to ride that V11 Sport, years before we met.

If we come to anything definite, I'll report back, but neither of us has much time or money at the moment and it's not her only vehicle, so it could be a while!

Cheers all,
J

Mine had a `white line` wobble and also a wobble at 55-60mph, I replaced the steering head bearings, they looked ok but the grease had gone really hard-this helped still had the `white line` wobble but the 55-60 one was almost gone.

I swapped from pretty worn bt45`s to avons-this cured the wobble over white lines-personally I think its because we run skinny rims and crossply tyres, I have a wider rear waiting for the next payday to get the correct 160/60/18 on it and I think a 18x2.5 with a 110/80/18 radial will help.

The 55-60 wobble has almost been eradicated bythe latest bit of post winter fiddling, I put new pads in and replaced the pins with stainless, the wobble is stlll there but I will take one or both hands off of the bars and not worry.

Hope this helps

Ray

A theory :

• I've experienced this once at a particular speed when I took my hands off ... I also tried to reproduce it at higher and lower speed but couldn't

• I can't feel any shake or wobble at any speed when I have my hands on the handlebars, even if i use only two fingers to hold the throttle

My thought are:

• Our bikes have a vibration induced by the motor at around 3000-4000 rpm

• the extent of vibrations is varied but probably related to how well the motor is running

It is possible that the wobble is due to these vibrations. In science these are called positive interference. When two vibrations are generated at the same time they add and produce a larger wave. We all know about army marching over a bridge... if they are in step they can cause large vibrations. These vibrations resonate and peak and will also disappear depending on the frequency (rpm) and randomness (being out of step).

I don't know how to prove this, but if you:
have vibrations at a certain speed (rpm), see if you have it above and below (say 20km/h above and below). If yes, then you have a mechanical problem, if not, it is induced by the vibration frequency, almost certainly the motor + tyre + speed??

Just a thought, but it is possible.

Jonathon you are spot on regarding the RT and winter riding and I can empathise with the lack of finances and keeping these bikes on the road as motorcycling can never be called cheap and then add the age of the bikes and it all becomes compounded.

As for the broken handlebar mount it is either broken or not and when it is, the handlebars are free to swivel on the other one so in short you will notice it but if they were starting to go??

There are a lot of variables in this equation and it may just be a case of eliminating them one at a time but the testing phase is what worries me.
I can tell you my front rim was not the roundest until it was repaired and the back is not too flash in that regard.
So keep us informed and be careful.

"I have a wider rear waiting for the next payday to get the correct 160/60/18 on it and I think a 18x2.5 with a 110/80/18 radial will help."

Ray would you care to expand on that?

If you have an older K-100 how do you plan on fitting that rear rim & tire?

Thanks,
Rick

When you check your GF's bike did you get her to sit on the back seat on the centre stand so as to lift the front wheel off the ground, if you are looking for any trace of binding in turning the bars side to side you need to get the weight off the tyre to feel it.
Regards,
K-BIKE

Ned,
You are correct about engine induced vibration on the 100's (not so on the 75's because of the balance shaft.) I have no wobble up to 100mph... beyond I don't know..I chicken out..! Old age I guess. I just make sure I ride above or below 60mph when slight vibration comes in.
My bet is still tyres.
I like the sound of beads introduced into the tyre when fitting new, I'll try that on my next set. First I have heard of them.
Ajays
Bike courier services love the RT's very popular here.

Finally_A_K wrote:"I have a wider rear waiting for the next payday to get the correct 160/60/18 on it and I think a 18x2.5 with a 110/80/18 radial will help."

Ray would you care to expand on that?

If you have an older K-100 how do you plan on fitting that rear rim & tire?

Thanks,
Rick

Personally I think our old kay`s are under tyred and modern radials wear and grip much better than skinny crossplys and way bmw`s are built quite a few diffrent wheels will fit diffrent bikes, I have a R1100rs rear wheel (18x4.5 takes a 160/60/18) in the garage ready to be fitted, There may be issues with the centerstand fouling the wider tyre but a k1100 stand should sort that out.

on the front you have a choice of 18x2.5`s k75s had one and you can use your original discs, k1100lt is the other option but it has 305mm discs so you would need to have your calipers spaced out, this allows a 110/80/18 radial to be fitted.

Dont hold your breath though, I have had the wheel since midwinter and still have my tyre money stolen each month!!! kids huh!

Ray

Hi there.
I had (hope) the near 60KPH wobble, so I could not leave the bar and "hip turn" the bike, and another wen going near 160KPH
So the rims were sent o check and align, tires changed and balanced.
As result the 160KPH one got cured, but the low speed one did not.
Talking to a friend he sugested to check de rear shock bolts. Those were not full thigth, once they were at spec torque the wobble dissapeared.
Now I can even stand up hands free
Best regards
JAP

Ray, I am encouraged by you're optimism, but that 160mm rear tire and 4.5" rear wheel will be difficult to install.
I just installed a fresh set of Avon radial tires on my 1985 K-100RT.
I installed a 110/80zr-18 front, and a 140/80zr-17 rear.
The rear tire just fit, it cleared the swingarm by 1/8", the stand was close too but not an issue.
The front was tight and required trimming down to the minimum the fender mounting bolts.

If you do fit up that bigger rear I would really like to be in that loop!
BTW that Avon tire combo was an AV55 front & a AV46 rear.
It went down the road like a dart...no shimmy, no shake, handles the radials like it was built for them.
Thanks,
Rick

http://www.bmbikes.org.uk/Forum/viewtopic.php?f=13&t=10607
you may have to regester to view the pics on this post.

I just sold a 3 spoke 17x 5.5 which would have taken a 180/55, not that would have had clearence issues!.

also Finally_A_K what rim have you on the front?

Ray

Ray, I checked out those 3 pics....I see the guy mounted the wheels, but like he said (I think) the rear wheel will be off-set from the front one, not in the same track line.
Is that right, or am I all screwed-up?
I just cannot see how center-line of the bike will be respected with a 4.5" rear....
Anybody else here done this?

As for my front wheel it is a stock skinny-minny 2.5" x 18"

Rick

Hi Ray,

I recently fitted a K1100 centrestand and I have a 130 tyre on the back. Any bigger and you may have some issues.
There is a fair bit of meat on the stand so could be ground off but I doubt if it will be a straight fit.

Ray, if I understand you correctly, you are thinking to fit 160 tyre on what is considered to be 140 max rear.

I just went through the process of fitting a new radial and I can tell you that 140 is the max I would entertain. It is almost certain that 150 will rub against the shaft hosing and 160 will not fit.

If I was really brave I could take a grinder to the shaft hosing and remove a few mm of casting ridge but that would be risky.

The radial that fits is Avon Azaro and if you can get them, Dunlop 2?? (205 I think). Many cross plays are available.

However if you manage to do it without changing hardware, I would be interested to know.

Ajays wrote:Ned,
You are correct about engine induced vibration on the 100's ...

...I like the sound of beads introduced into the tyre when fitting new, I'll try that on my next set. First I have heard of them.
Ajays....

Well it was a shot in the dark. Thinking about it, I say that if the vibrations have anything to do with it, it is minor and possibly only to initiate the wobble.
My experience was that the bike was pointing down hill at around the speed suggested ... i took my hands off to adjust my helmet or some such and got a shock on my life. I can't understand why I couldn't feel anything through the handlebars ? Strange.

beads? any links?

maybe this will help:

http://www.randakks.com/TechTip87.htm

Looks like some good info although I am a little dubious about the three pound counterweight.

Sounds like a problem they could not fix and as luck would have it bunging a weight there and calling it a junction box did the trick.

Ned,
Try this. http://www.dynabeads.co.uk/autobike.php
Ajays

My K100 RS 16 Valve has never shown a hint of wobble at any speed one hand or two even with as Ned says just two fingers holding the throttle open.
Regards,
K-BIKE

I just cannot see how center-line of the bike will be respected with a 4.5" rear....
Anybody else here done this?



Rick[/quote]

It appears that bmw Kay`s have always had a offset centerline through the wheels, I will addposts later(just started a night shift-boo!)

Ray

Ray, I'll look into that bit....
Easy enough to do, a builders square and a chaulk line will tell the tale.

I'll post my obsevations.

Rick

Hi Jonathon
I'd like to add road surface to your list if I may
I've had the odd wobble due to an uneven road surface and maybe councils
are skint nowadays but the roads seem to be in pretty poor shape round here.

I know its an obvious point but Ive been caught out by a few hard to spot sunken sections and channels
that caught me unawares and had me gripping the bars nervously.
Otherwise I've found my K to be a very stable machine and rarely have to hang on grimly.

Yesterday riding on some quiet country roads with good surfaces I made some cautious experiments
and I found I could let go the bars whilst decellerating at speeds from 40 to 80 mph.
Bog standard, well used, BT45's fore and aft.

I hope you find and fix the problem with your gf's bike
Its unnerving to have a bike start wobbling under you and I wouldnt want to ride
one that did that either.

Reg