Did you find the fault ?

Sounds like impropperly installed tires... or rim problems...

__________________
Drive Safely,
Albert

My R100RT has a vibration problem as well, as soon as I go past 130kmh it starts to buzz, up to 140 and it starts to smooth out again. I had the top end rebuilt new pistons big ends and little ends and conrods balanced, carbs rebuilt and balanced. Crossing the nullarbor with four other BMWs and they sitting on 130 was a pain in the butt right in the buzz zone! I have spoken to a few others that have the same problem, my bmw only mechanic said that there are a few he has come accross with the same problem, and thinks there may have been a harmonic problem with a batch of crankshafts from the factory. I just have to put up with it until I do a full engine rebuild and get the crankshaft assembly balanced together.
Rob...

Sorry Rob - have missed what year your engine is made.
The word buzz confuses me a bit to - is this what you mean?:
From Wikipedia, the free encyclopedia
"A buzz can be a rapidly oscillating two-tone noise caused by vibration or other source, such as that produced by bees or wasps. It can also refer to a generally excited hubbub, or background noise - i.e. a crowd at a sports event can "buzz."


Sounds really weird - please explain more; and please explain what problem it causes you, you only state that is it "...pain in the butt...".
You have used, vibbration, and then buzzing - sounds like two different things happening at the same speed and/or rpm.

Wasn't your heads dual-plugged? Do you have the timing spot on - i.e. one position or is it off by 1-1½' between the "sparks" ? When I put in the stops in my ITU I think I damaged one of the springs just ever so little - my timing is off by about 1½' causing some unevenness in the running of the engine that I did not have prior (= will fix it later).

__________________
Drive Safely,
Albert

Hi Albert
Its an early 83 model. Buzz and vibration are the same just a different word same meaning in the English language. The mechanic who services my bike has done many twin plug conversions and there has never been a problem with any of them. I have absolute faith in his work, people come to him from all over this country just to have him work on their bike! I bought the bike when It was one year old and it has always had this problem. In the early days I had it serviced at the local BMW dealer (Tom Byrne) in Sydney and they told me that there were a few others (1000ccmodels) that had a similar problem. After a few years Tom Byrne relocated and the old mechanic retired, and they seemed not to have any interest in the old boxers anymore so I switched to Don Wilson another well respected mechanical workshop with a history in racing R serise BMW,s they said the same thing, some R100's from around my bikes vintage had vibration problems due to crankshaft balance from the factory! I have done a lot of rallies over the years and as sutch spoken to many R100 owners some say their bikes are the same some dont, I can only assume that they ride below the rev range that this occurs. I did not really worry about it too much over the years myself because it only seems to happen once I go over 125 kmh I mostley travel at about 110-120kmh. It was only when I crossed the nullarbor between Adelaide and Perth a long straight road and sustaining a speed around 130-140 to stay with the group that it really anoyed me, if I went up past 140kmh it dissapeared completely, no vibration? I have had this bike for 24 years and I love it as much as the day I bought it. I can live with it until I get a complete engine rebuild and either get a new crank or get mine balanced, but with the amount of riding I get to do these days Ill probably die first!
Rob....

Hi Rob,

The 1983 were the best in my eyes.

What vibbrates?
You have neatly dodged that question -

In comparison - my 1984 have a skeved(?) and oval cast front-rim... it tends to vibbrate like a ... Cobra at 120-128km/h.
The engine have a "rocking" sound, like a steem-engine-lokomotive at 130-150km/h.

Once the engine mounts had vibbrated lose... the bike sure vibrated then...

Have you seen with your own eyes that the ingition timing is on the spot ?

Have you seen with your own eyes that the carbs are correctly tuned/balanced?

I had to install handlebar vibration dampers - 300gr/each which is not enough... 500gr would probably do it.

I have heard of bad cranks before. Never seen one. Never met anyone with personal experience of one for certain. What I have seen a lot of is poor service, really outstandingly poor, done by top notch mechanics locally. Needles at different hight/position. Damaged diaphrams. Wrongly set valve-play. Compression losses. Damaged nicasil lining. Leaking heads. Loose butterflyvalve. Wrongly set butterfly valve. Leaking carbs; dome/lid, choke, o-rings gone. Lost vaccum screw. Smashed down-pipes. Leaking air-filterbox. Reed-valve oozing engine oil - gooeying carbs. Missing bolt inside air-filterhouse - hypoid leaking gooeying carbs. Different size mufflers/silencers. Malfunctioning ICU's, coils and ITUs. HT-leads bad. Wrong plugs, and bad plugs. Loose steeringhead ballbearing. Loose wheel-shafts/axels. Worn wheelbearings. Poorly grease wheelbearings. Worngly set tires. Wrong tires. Wrong air-pressure. Worn out-put shaft in gearbox. Loose 5th sprocket/gear - ocillating on the shaft. Bolts loose on shaft. Pinion loose in bevelbox/final drive. Wrong play in bevelbox. Worn main bearing in bevelbox to crown wheel. Bad splines in shaft and to wheel.
... I've seen just about all... and these have come straight from major overhauls at really respected and well known mechanics/garages... Hence I do tend to be a bit sceptic.

There is a basic bit in your problem that does not ad up yet - the speed.
If you change gear you will have this problem occur at different speeds in accordance to the revs (if 33/11 and stock 5th - about 5000rpm at 130km/h if I recall correctly) if the problem is related to the crank/engine... you have not mentioned if this is so, or if the vibrations are isolated to the speed.

Vibrations can really be annoying... K100 could not be driven at 110km/h as we have in Sweden. 105 or 120 were ok. My Suzuki could not be run at 120 but 125/130 was ok. I know this problem all too well. Hence my interest in trying to help you find what causes it in/with you bike.

__________________
Drive Safely,
Albert

No not bad work, he allows you to watch even help if you want to, so I see everything he dose. I will be taking the bike to the roadworthy inspection station tomorrow ( it has been off the road for the last 12 months ) I will get it registered next week and take it for a run and get some more detailed info for you. IE rev count at certain speeds ect. its been a year or more since I rode it for more than a 100 kilometers or so, so Im a bit forgetful of the speeds and what gear ect. I had the gearbox bearings replaced and a new clutch installed about 20k ago so I would discount them as being a problem. Like I said I bought this bike when it was a year old and it has done it from day one, I rarely ride in that speed range so It has not bothered me too much over the years.
It is a high frequency vibration that I feel through the foot pegs and the handlebars mostly, it makes my hands numb I ride at that speed for more than half an hour or so, its not like the rough feeling you get from a bearing going bad, its a balance problem somewhere and my bike has been pulled right down except the crank has never been out of the case, its the only thing that has not been examined.
Thanks...Rob..

Hi Rob,

Sounds like a mechanic that I too would trust! -

What you can do is to check that the tires are set properly on the rims - there is a marking/line that goes around the tire. It should be at an even distance to the rim - if not => bad vibbrations.
Then check the rim - just lock the frontwheel (straps crossing over the tank to either side frame will be good enough). Put something next to the rim that will allow you to see if the tip of a screwdriver (or similare; pen, stick, whatever) follows the rim at the same position all around; and if the rim is skeved or straight.
To do the same with the rearwheel - you need to weigh down the front end; here an assistant will be handy to have.

If these two simple tests pass - you can be fairly sure that the wheels are ok.
It is very rare to have wheelbearing problems causing bad vibrations; but it can happen. Spinning the wheels installed wont do it, but will give you an idea of if something may be amiss. When did you change the seals and regrease the wheelbearings last ?

When you turn the rear wheel back and forth - any noice, rattling, spocket "chewing" ? How does each part of the transmission sound (large screwdriver pressed against the tragus (ear) and against the site on the bike where you want to focus the listening) ? The bevelbox should be "silent" and the shaft should only have a sound of the joints "snapping" over. Any suspisious sounds from the bevelbox may indicate worn bearings or too worn splines.

As for the gearbox... Oak Oshlen wrote about it in ABC Newletter back in early 1990:ties. Best way to test is to secure that the rearwheel is spinning freely in the air = strap down the front-end.
Start the engine, let it run at 3000rpm and put it in 1st - moving up to 5th and tehn back down to first and neutral. If there is a bad bearing in the gearbox you will hear it! Sounds like the rumbling sound of the machines at quarries grinding rocks. If uncertain - use the large screwdriver again; a bad bearing will jolt you backwards. Thats how bad it sounds.

Loosen the gaiter/bellow on the shaft at the gearbox. You need a 10mm wrench(?) - just feel that the four (4) screws/bolts securing the shaft to the gearbox are tightly set (put the gearbox in 1st - you will not be able to stop the shafts movement by holding the rear wheel). These bolts are stretch bolts and shoudl be renewed everytime the shaft has been removed... I have opted to use wave(?)-washers instead - never had any bolt gotten loose since then. If you want to play it safe - see to that you have a set of new bolts and change to them; to set the correct torque is awkward due to the limited amount of space; I simply use a short 10mm wrench (10cm or so) that will not give me too leaverage.

The swing bearings should be regreased at least once a year - using a greasegun. If they have not been regrease for some time... you need to take off the swingarm and pull the bearings.. this will damage the seals and you will find it easier to buy new bearings... fill the hole with grease (some swingarms lack the steel lid in the bottom of the left side - make one and install it.

Also check the stearing bearings, steering damoer, and attachments of the rear shocks. When did you last overhaul the rear shocks and forks ?
Rear chocks shoudl be overhauled every 3 years or 30-50 000km. Forks should have new oil at least once a year ( I use Omega 699 automatic gearoil 5W/20 = same damping cold as warm => more predictable tracking and better damping). When did you last pull the springs from the forks and measure that they do hav ethe same length ? If you could you should also check that they have the same strenght. There tend to loose power and lenght over time... and can cause a wobbling tendency as well as vibbrations...

Check that the rear frame is securely bolted to the main-frame - never seen one to be loose, but it could happen.

Is the enginebolts/rods/axels tightly pulled ? I did check mine - still as I mentioned they became loose...

What you can not check so easilly is the clutch. If the clutch has been impropperly assembled you may encounted vibbrations like you describe - never seen it, but heard lots of reports on it and claims by owners that they have suffered it. This is... how can it be incorrectly installed ?... I've tested to deliberatly not reinstall the clutch with the old markings and have not experience any extra vibbrations... I know I could be lucky.
Remeber that the clutch is supposed to be balaned and if reassembled one position off could result in unbalances causing vibrations.
A worn clutch-plate can cauese vibrations.

Looking forward to your road report and hoping dearly that you will discover the vibrations to be speed related and not rpm related.

__________________
Drive Safely,
Albert