The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: georgesgiralt on September 30, 2013, 09:03:05 AM
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Hello !
Last week, I was running my '82 R65 and got a big bug on my screen.
I left the handlebar live it's life and opened the helmet (using both hands).
As the "cruise control" screw was not free, the bike continued to ran at the same speed and course. (around 50 ~60 km/h)
I was very surprised to see the handlebar oscillate more and more and I had to stop it before it slap the tank.
As I had a very worn out rear tire, I changed it, checked both tire pressure and did the test again. Same reaction.
Front tire is a Lasertec at 2.1 bar pressure (as per Metzeler specs) Rear is a ME77 at 2.3 bar.
The steering bearing had been greased a couple of months ago and the play adjusted. they are fine. Rear shocks are Fournales OPS at 9.0 bar pressure.
So what should I check ?
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I don't think your experience is that unusual. Even one hand on the bars would have been enough to damp any tendency to oscillations. Assuming the wheel and swinging arm bearings are correctly adjusted what that's telling you is there is a need for some damping in the steering system.
How much pre-load do you have on the steering bearings, just eliminating all play is not enough. There needs to be some pre-load usually judged by the rate at which the bars fall from side to side but not so much that it produces a low speed weave through over correction inputs to the bars. The safest setting is as much pre-load as you can apply without inducing a low speed weave.
Maybe there has been some bedding in since you greased the bearings and they need tightening a touch.
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Thanks Barry,
As I've changed the clutch recently and a couple month later opened the gearbox to replace the selection spring, I'm quite confident that the swing arm bearings are properly greased and adjusted...
I feel the steering head to be too loose but a mechanic I know says it's good.
So I will try to tighten it a bit and see what change it make...
BTW, how do you tighten the curled big nut ? By hand it seems I can't go farther than it is.
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I have a head shake on my R65, but it's more common at about 45 to 50 mph, so almost twice as fast.
Makes it quite interesting to reattach the velcro on my cuff while at speed.
I've mentioned it to my mechanic (who does race setup on weekends and really knows his stuff) and my head bearing is fine. In my case, it could be exacerbated by the fairing. My rear shock could stand to be replaced, so that could be a factor too.
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BTW, how do you tighten the curled big nut ? By hand it seems I can't go farther than it is.
I tape some cloth pads on a pair of slip-joint plumbers pliers and get after it. No marks. No errors.
Properly adjusted for preload, the forks should fall gently to full lock. Not hard enough to make a big "clunk". So sayeth the guru on the mountain top.
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I feel the steering head to be too loose but a mechanic I know says it's good.
Unless your mechanic rides an airhead I wouldn't listen to him.
This is a safety issue at least as important as wheel bearing pre-load and look at the fuss we make about that. BMW prescribes the same approach to head bearing pre-load using some special measurement device that nobody has so that's why we use the "bars falling gently to the stops" method.
There should absolutely be some bearing pre-load to provide damping. When you have it right you should be able to feel an increase in resistance to turning the bars over and above just eliminating all bearing play.
Bear in mind the pre-load changes when you tighten the top screw so some experimentation is usually needed.
The adjusting ring is a daft bit of design as you have almost no hope of tightening it adequately by hand. It should have had the slots for an adjusting tool just like other airheads.
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Please bear in mind that this is a short wheel base airhead. When the first R75 was released, it also had a short wheel base and suffered from complaints of a slight instability - the result was a lengthened swing arm and the longer, larger capacity airheads.
But the main difference between the R65 and its larger rivals is again the swing arm length. The fork rake and trail is the same or very, very similar. But it has the shorter swing arm, which is why the rear shocks are different length to those fitted to R50/60/75/80/90/100.
Check your bike over thoroughly and make sure that everything is working as it should be, then rejoice in the fact that you have nimble bike, rather than a long, lazy tourer. The bike was originally marketed as a mid size bike with mild sporting pretentions.
When I rebuilt mine all those years ago, as a café racer, I also found a little wayward/playful wag of the handlebars at certain speeds, especially when I was having fun. I thought about a steering damper, but as the 'wag' never manifested itself as anything more sinister, as long as I was holding the handlebars, I never bothered. I am not sure it even does it now. But that might be because I running a 19 inch front wheel rather than an 18 inch one
If a little head shake still bothers you, buy the BMW steering damper. Otherwise put it down to a little exuberance.
Cheers
Rev. Light
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I get a bit sometimes in mine with the side car on now, but only in specific cases, like accelerating briskly while turning left onto the road as it crosses 40 mph or so, and hits just the right bumps. Going straight down the road, I can let go of the handlebars for a bit, it goes surprisingly straight, considering the side car, and no headshake. My 2010 Rocket Touring, on the other hand, has always had headshake since new, and front tire premature scalloping, my dealer helpfully said "that's just the way they are". [smiley=rolleyes.gif]
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I also suggest a check for the proper steering head bearing preload, and, if that doesn't bear fruit, try first adding a bit more air to the front tire - You are only at about 30.4 PSI, I generally run mine at 34-36 PSI, and I KNOW that if it drops down to 25 PSI I will get a brief weave/oscillation as I approach 35-40 MPH.. I do have different tires (Bridgestone BT45) and I have progressive (stiffer) front fork springs and rear shock springs. you might also try lowering the pressure slightly in your rear shock absorbers - sometimes these wobbles are not due to loose bearings but from mismatched suspension compliance.
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For anyone interested I had a look at the BMW method of setting the head bearing pre-load. This is one example where the BMW manual is not useful as it gives brief description of the method then fails to provide the actual torque value needed to carry out the test.
As far as I can make out the method is to apply a temporary stop that restricts the steering lock to 20 deg which is approx. half travel. Then a torque wrench is used on the cap screw to measure the force required to return the forks to the centre position. Snowbum gives the setting as 2.6 ft/lbs . I don’t have a torque wrench that would be reliable at that setting so unfortunately I can’t try it.
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2.6 ft/lbs ....
Hu ho...
As I'm far from confident enough on Imperial units, can someone more knowledgeable translate this in mN or mkg ?
Mani thanks in advance !
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3.5 Nm
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It's what I thought.
I've a small torque wrench. Have to look at the minimal setting, but I doubt it can go so low a figure... It's a torque screwdriver's value !
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Snowbum gives the setting as 2.6 ft/lbs . I don’t have a torque wrench that would be reliable at that setting so unfortunately I can’t try it.
Wrap a wire tightly around your favorite 1/2" cheater bar and bend a hook onto it such that the centre of the hook is 1 foot from the centre of the allen key socket. Tie a piece of string to the hook and the other end of the string to a reasonably accurate spring weight scale - the type you buy at fishing shops for weighing fish. 2.6 lbs on the scale at 1 foot along the cheater bar is 2.5ft/lbs of torque at the steering head..
Having said that i have an opinion that head shake is usually due to a tyre mismatch, a frame alignment problem and sometimes a suspension problem. Forgive me if I am wrong, but isn't the Metzler lazertech a radial and the me77 a crossply? If so, the differing reactions of the tyres could set up a shake right there.
I once tried a set of flash dunlops on the RS and it developed a terrifying tendency to tank slap at 60kph that disappeared as soon as I changed the tyres. There was nothing wrong with them, they ran just fine on something else I owned, the BMW just didn't like them at all.
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So my smallest wrench is from 8Nm up to 54 Nm.
Not fit for the job.
I've to ask a co-worker which is a fisherman if I can borrow it's fish weighting tool 8-)
As per the Lasertech, I do not know what structure it is. All I know is that the seller had only one suitable tire that day and it was this one, V speed rated and very expensive. As the ME22 was cut open by a piece of steel found on the road, I had no other alternative...
When the new ME77 will be worn out, the lasertech will be too. And at that time I'll fit a couple of Michelin Pilot Activ tires. A couple of friends o f mine use them on an old Guzzy and on a 1000 RS with great pleasure.
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If we analyze a wobble we need:-
A system that will oscillate - that's whole steering asembly (and sometimes the whole bike)
A positive feedback source of input energy into the system - that's the tire. No question that tires are the source of wobbles in this respect.
The interaction between the tire and the road surface is the energy source for a wobble and that input is always there at a very low level. If we remove all sources of damping by taking our hands off the bars then under "certain conditions" the wobble can increase in magnitude so that with each cycle providing more positive feedback the wobble develops to tank slapper proportions.
It's the "certain conditions" that we need to address and that can be one or more of the things that have been mentioned like tire condition, tire pressure, head, wheel or swinging arm bearings or even weight distribution. So I don't think you can always put a finger on one specific source of a wobble but what you can do is provide the best circumstances for it not to develop by having some damping in the system to absorb the energy. That's why the steering head bearings were designed by BMW to have sufficient pre-load to provide that damping effect.
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I've checked the tires. No "Radial" marking on the Lasertec so it seems to be diagonal.
But, both tires where made in Brazil. So the source of the Salsa is definitively the tires :D 8-)
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I just read the BMW maintenance manual for the R45/R65 I bought 30 years ago.
On chapter 31 they explain how you change the bearings on the steering columns,
and at the beginning of chapter 32 they give you the torque value for pre-load :
In 1978 there is no value given. then at the first update, in 5/80 they give 35 N.cm +/- 20 and at the second update, in 8/82 they give "no play" ....
So this seems to be a very controversial figure ;-)
Nowhere they explain how to measure the torque and or adjust the play/pre-load... Unless I've lost some pages on the loose sheet binder ;-)
Maybe it's something they taught at the school for all bikes and that the value was specified then.
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My BMW manual has the method but not the torque figure. I got the 2.6 ftlb from snowbum.
Got to say I'm surprised that they reverted to a no play setting. This is a safety critical item and if a little pre-load is safer without impacting on steering response (and it doesn't) why would they opt for a less safe setting. The other issue is a "no play" setting is near impossible to set precisely especially with the weight of the forks and wheel on the bearings. It's almost inevitable you will end up with a little play or a little pre-load. Better to aim for the pre-load.
I suppose it's possible that 81 on models with the slightly longer wheel base were judged to be more stable and therefore not in need of any steering damping. Can't think of any other logic for the change. On the other hand the 81- on riders manual still talks of having the correct pre-load set.
It doesn't add up. Maybe it's a translation error.
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I am not aware that the post 81 wheel base is any longer than the 79. There are no changes in the forks /frame/shocks or swing arm?
Just because I am unaware, does not mean it isn't true. Just never seen any numbers...
Changes in procedure for servicing and policy can happen for a multitude of reasons, not all technical.
It amazes me how policy and procedures change even for things like medical and First Aid? Over the years with the various jobs and hobbies I have had, it has been necessary for me to take first aider courses at various time - it is amazing how the Human body has evolved over the last 30 years, as the courses, have changed a heck of a lot! No more mouth to mouth, I am surprised they have not changed the recovery position.....I digress.....Sorry
Rev. Light
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We are talking just a few mm but there is a small difference in wheelbase. The figures I have from the riders handbook are 1390mm (54.7") for the early model and 1400mm (55.1") for the later model. The subframe swinging arm and drive shaft are all different part numbers. I doubt it makes much practical difference to stability though. I was just clutching at straws trying to think why they would relax the pre-load requirement.
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I just finished retightening my steering head bearings after my restoration because after several hundred miles it developed the high speed wobble. At the time of the restoration I thought I had the bearings as tight as I could get them even though the side to side "falling" of the front end was too quick and hit the stop too hard. I also had a clunking sound over some bumps. I used pliers similar to what Monte mentioned and was able to really get a grip on the large ring to the point that it was too tight. As previously mentioned when you re-torque the top two triple clamp bolts and the center bolt your bearings will be further compressed. It took me about a dozen tries to get it to what I believe is right. Good luck, Dave 2
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So, I've modified a bit the pre load. Have to test ride the bike, though.
I used a very large falt screw driver and a rubber mallet to turn the big round nut. At first, after tightening the centre nut, the steering was very stiff. So I slackened the centre nut and did it again.
I could not turn the nut with my plumber's tool. too small. So I decided to go the screwdriver way. Doing it gently and lightly I did not mar the nut.
Will report back when I've ridden the bike.
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I'm an happy rider !
Same place as before, same speed and same conditions : the bike runs strait. No wobbles !
On the highway if I leave the handlebar leave it's life, the bike also runs strait...
And no oscillations when running right. So the pre load is not so bad.
The steering falls easily on the right side, but not so easily on the left side (I think my electrical harness is not routed correctly, and if someone can provide a couple of pictures as per the correct routing, it would be perfect)
I'm happy ! :D 8-)
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Also check the engine to frame mount nuts. I had a disturbing low frequency wobble in fast curves that was corrected after adjusting the front engine bolts and nuts that where a little loose.
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Victor! Where have you been? After hanging out with you at the MotoGP in Austin, I thought you dropped off the edge of the earth. Glad you're still above the grass. ;)
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Hi Monte:
Lot of work and just plain lazy.
But it nice to be back
I'm truly enjoying my bikes.
The K1100 is a dream to ride in Mexico that has few and far between highway patrols.
I let it loose and just grin.
But the R65 is my daily ride pride and joy.
The carbs are perfectly balanced and it just purrs along accelerating at its nice predictably strong pace. The valves play their music when cold and just enjoy the sound of the engine when it's at its proper temperature.
It's still the only airhead in town and maybe the state. All my friends are just amazed that it's that old and still going strong.
Looking for a R80GS but need to catch my wife off guards.