On my '91 K100RS 16V, 85k miles:
At idle, in neutral with clutch engaged, i.e. gearbox is spinning, there really seems to be a lot going on in that box. Just mechanical whirr, no knocks, rattles or rumbles. And nothing noticeable on the move. Now it's a long time since I had a bike that was this quiet, well silenced, no top-end clatter, no induction roar. But I can't remember the gearbox being as noticeable on, say, a CBR600. Goes away when clutch is pulled in so definitely down to those shafts a-spinning.

I'll add that it's had a new clutch, new seals, everything tight, splines greased etc. And yes, the gearbox has oil in it. There was a bit of water in the gear oil when I got it, and it had been standing for 4 years before that, but I've seen a lot worse. On the bench, rotating the input shaft by hand, you could definitely hear the gears turning but again, not really any different to other boxes.

So I'm just trying to gauge what I'm hearing. I am mindful of all those straight-cut gears spinning away on three shafts and it wouldn't suprise me if "they all sound like that". But confirmation would be appreciated.

I've never heard a quiet one yet. Two skeletons having it off in a tin bucket comes to mind.

What Rick says. Straight-cut gears are noisy by definition.

It might be time to unpack the otoscope. 

I've actually been meaning to make a post about this! Mine didn't used to whine but since it passes the 80K mile mark there's a noticeable whine in all gears.. Normal or time for an oil change?

THought the K-bike whine was patented by BMW. All of mine have. K100, 2 K75's.

First time I encountered a K was in the mid-80s as it pulled away from Creg ny Baa during the TT. And I was stuck by the elecric motor-like whine, very different and noticeable because otherwise is was so quiet. Maybe airhead BMWs and bevel twin Ducatis would sound the same if the general row was removed.

Can't say I notice that gear whine on my 16V when driving along. Think I'll have to go somewhere where Ks gather and compare. But I haven't seen a K out and about for years. Mind you, I've only seen three running airheads in the past 2 years. There used to be a BWM owners meet at the TT, is that still going?

lots of us Ks still around, problem is you don't see or hear us coming(stealth mode) just that Ksound when we are gone. Some of us get to Horse Shoe Pass now and again.Coffee and chat should you spot us   
Don't know about BMW TTClub/meeting.

moriarti wrote:lots of us Ks still around, problem is you don't see or hear us coming(stealth mode) just that Ksound when we are gone. Some of us get to Horse Shoe Pass now and again...

Horseshoe Pass is a regular route for me, although mainly under pedal-power. Always seemed to be Repsol Fireblades and 1200GSes but now I know, I'll keep a look out. Maybe I'll see you there. Thanks

Not that anyone can go there at the moment of course.

No... and next year's Dragon Rally is cancelled...

Couple of things not cancelled BILLS RAIN and hopefully BREATHING.Just got back from a ride,like a drowned rat.Ha Ho Happy Days

I put  a tea spoon of Molydenum disulphide powder in the final drive and gearbox on my K100LT. (Prescribed and dispensed by Dr. BobT) it made a bit of difference to the noise and smoothness of both.
Worth doing if you can get it in a small quantity.

88 wrote:I put  a tea spoon of Molydenum disulphide powder in the final drive and gearbox on my K100LT. 

John Muir, author of HTKYVWA–AMFTCI, prescribed that for VW transmissions in 1969. I was one of his votaries. The transmission always performed flawlessly when I pushed the bus out of traffic to the curbside because it stalled.

Laitch wrote:

88 wrote:I put  a tea spoon of Molydenum disulphide powder in the final drive and gearbox on my K100LT. 

John Muir, author of HTKYVWA–AMFTCI, prescribed that for VW transmissions in 1969. I was one of his votaries. The transmission always performed flawlessly when I pushed the bus out of traffic to the curbside because it stalled.

I had that book as well. One thing he never covered was how to keep the clutch cable on the split windshield bus from freezing in the tube in the winter time. Several were the times I had to drive home without a clutch in the dead of winter.

stanthomas wrote:
There used to be a BWM owners meet at the TT, is that still going?

No idea but I did get the longest distance award.  1990, I think.

TacKler wrote:

stanthomas wrote:
There used to be a BWM owners meet at the TT, is that still going?

No idea but I did get the longest distance award.  1990, I think.

Little did I imagine that the event in question might be the TT itself:
Manx Radio 4 October
... strange times.


Getting back to the point, I've changed the gearbox oil and it's much quieter. What came out looked more like a 5 year oil change, not 1 month and 200 miles. I had flushed the gearbox with 10/40 while it was on the bench to try to clean out water and residue from it's 4 year 'rest'. Perhaps some of the 10/40 was left in the box and thinned my first fill.

Anyway, the box sounds much more normal now and not something I'll worry about. Another oil change planned after 500 miles to flush out more of that residue then fill with synthetic.

Thanks for your comments.

stanthomas wrote:I've changed the gearbox oil and it's much quieter.

Now this is interesting, probably time for me to do the same then!

Do not use synthetic oil for final drive or gearbox use ep80/90 it will be more than good enough

#18.Where angels fear to tread :sunny1:For  the past 20 odd yrs iv used standard gear oil with a dash(300ml) of Moli slip additive,Resulting in a quiet silky positive gear change It works for me.

From what I understand about these old K bikes is that the bulk of the whine comes from the alternator. I wouldn't think you would hear much whine from the tranny or rear end if they where in good shape.

To come back to this, I finally changed the oil in the gearbox and the whine is reduced although not completely gone. The magnetic drain plug had a bit of an afro but not too bad for having done 10K miles so I'm not worried about it, it may just be that they start to whine a bit after 80K.

cycleman - this is definitely gear whine from the box, some gears are louder than others.

stanthomas wrote:First time I encountered a K was in the mid-80s as it pulled away from Creg ny Baa during the TT. And I was stuck by the elecric motor-like whine, very different and noticeable because otherwise is was so quiet. Maybe airhead BMWs and bevel twin Ducatis would sound the same if the general row was removed.

Can't say I notice that gear whine on my 16V when driving along. Think I'll have to go somewhere where Ks gather and compare. But I haven't seen a K out and about for years. Mind you, I've only seen three running airheads in the past 2 years. There used to be a BWM owners meet at the TT, is that still going?

3 of them beside my back door....out and about all the time!! I think they have all passed your house too.

92KK 84WW Olaf wrote:

stanthomas wrote:First time I encountered a K was in the mid-80s as it pulled away from Creg ny Baa during the TT. And I was stuck by the elecric motor-like whine, very different and noticeable because otherwise is was so quiet. Maybe airhead BMWs and bevel twin Ducatis would sound the same if the general row was removed.

Can't say I notice that gear whine on my 16V when driving along. Think I'll have to go somewhere where Ks gather and compare. But I haven't seen a K out and about for years. Mind you, I've only seen three running airheads in the past 2 years. There used to be a BWM owners meet at the TT, is that still going?

3 of them beside my back door....out and about all the time!! I think they have all passed your house too.

Doubt you've been past my house, it's a bridleway more suited to GSes; not that I've seen one of those go past either, just knackered old DT175s. Did see my first  brick for many a year about a week ago, a K100RS 8V at the A49 lights just outside Northwich.

To go back to the box, it's like a very loud ssshhhhh sound. Sometimes I confuse it for the cooling fan - until the fan kicks in for real. Sounds like a lot of shafts and gears tunring away in there. Very noticeable when I pull up outside the metal door to my garage, less so in the open.

stanthomas wrote:Very noticeable when I pull up outside the metal door to my garage . . . 

It was whirrey but now it's ssshhhhhey. Is it ssshhhhhey when it's idling in front of your garage door?

Laitch wrote:

stanthomas wrote:Very noticeable when I pull up outside the metal door to my garage . . . 

It was whirrey but now it's ssshhhhhey. Is it ssshhhhhey when it's idling in front of your garage door?

The sound is the same, just trying to find the words to distinguish it. I'm familiar with the whine from straight-cut gears and it's not that. And yes, when idling after the engine is up to temperature - don't hear anything above the wind, induction and exhaust on the move. I assume the garage door is reflecting the sound back at me making it much more noticeable but it's there even at the back of Tesco's car park. And this with my helmet on. I don't have to crouch down by the side of the bike for it to be evident.

It is more apparent than other bikes, even water-cooled Hondas, and I wonder whether this is normal for the breed and it's simply more noticeable because the rest of the engine is quiet or whether it suggest something not right after 4 years of lay-up with some water in the gear oil. But I guess I'll just ride it and hope it doesn't get any worse; for now, the bike's got some serious handling problems to sort out

You might be hearing an alternator bearing. Put your long-shanked screwdriver on it and listen through its handle.

Noise related to engine speed.......possibly alternator or input side of gear box or engine output or engine components like oil/water pump. Test on this one, pull clutch, hit rear brake and noise remains.

Noise related to wheel speed.....output side of gear box or final drive. Test on this one is pull clutch, hit rear brake and see if noise stops.

Definitely gearbox - pull in clutch, noise stops, let out clutch it's back.

I've not studied the box but I think in neutral both input shaft and intermediate shaft will be spinning together with all gears. I should run it up on the centre stand to check whether there is any difference when in gear.

Now it's not a bad noise, just noticeable and, to my mind, out of character with the rest of the bike.