Heat and the Klunk

[TA]

I have been noticing the klunk (technical term:) when shifting from neutral into first gets more pronounced as the bike gets up to temperature.  I don’t have an answer as to why.  Clutch drag produces this feature.  As the oil is getting warmer its viscosity is getting lower.  I would have thought this would help soften the klunk.  I did have new clutch fluid put in thinking there might be air in the line.  But nothing changed.  What else should I consider?  Heat is altering something.

[richtea]

The lower the viscosity, the faster the clunking item moves to hit its destination?

[Phmode]

This in one of those cases where 'they all do that sir' is actually true for unmodified bikes.

On both my K12 and the K13, giving it a few more seconds with the clutch disengaged before snicking it into first smoothes out the jolt amd the noise can only be hear in the next town, not the next county 

And remember, at lights, holding the clutch lever in is beneficial to the clutch lubing system.

[TA]

  the slip on ice gets you over the edge faster.  I’ll remember that the next time I’m talking to the Hells Angels about clutches. 

Un modified bikes can be heard in the next town....  my local noise bylaw enforcement officer would like to know what is modified?

Is my right leg getting longer?

[TA]

Richtea, I thought you were just throwing viscosity out there as query, possibly tongue in cheek with the ?  But I looked at the oil distribution records and went for a ride.  I always use the same route.  At the same points along that route the clunk began to progressively return.  The engine was heating up and as you said, more oil, lower viscosity, was moving through the clutch pack.  So I’ve taken steps to reduce the flow and will see how it goes tomorrow. 
A question, why did BMW change the oil specification from 10w-40 to 5w-40?

[richtea]

Not tongue in cheek, I'm just not sure how much effect it might have. I just remember that you chuck thick gunky oil in old cars before selling them, to silence them. In your case, it might be the reverse effect.

> A question, why did BMW change the oil specification from 10w-40 to 5w-40?
Not sure on that one, sorry. Before my time.
 
(BTW, my tongue in cheek is usually followed by a stack of  . It gets used a little too often, oops.)

[TA]

I’ll bite my tongue! 

[Phmode]

Terry. Oooh! Not at all sure that reducing oil flow to the clutch is a good idea. The klunk, whilst annoying and embarrassing at the lights, is a small price to pay to have the clutch lubed.

And if you hold the lever in at the lights the klunk is barely there.

Richard. Remind me never to buy an second hand bike from you...

[Andym535]

... I looked at the oil distribution records....

Just curious, but how did you do that?

[TA]

Having watched videos to do with the K12R and k13 clutches, especially Patrick Hofmann’s and 404’s (sharealike1), it’s apparent oil distribution is a problem.   The individual plates can go from soaking with oil to completely dry within the same pack. 

I was into my K12 clutch, my K13 clutch and most recently an unused 2015 clutch pack.  The pattern of oil throughout all packs was very similar.  The exception being the hub area of the K12 where the first hole was not low enough.

Making small changes with the steels and/or hub, I will go for a ride along the same route.  Returning and immediately get the clutch out and on the bench, 12 minutes.  The judgement of how much oil is on an individual steel is subjective but it is relative.  So I’ve been trying to even the oil distribution out.  The structure of the hub is a big challenge.  I always run the bike with the clutch disengaged before shutting her down.   Also should mention that I upgraded the oil pump.

The photo shows how I’ve been keeping track.  The heavy bottom line is the hub.  The heavy upper line is the pressure plate.  The horizontal lines are the steels with the spaces being where the oil holes are.  One hole delivers oil to the bottom of the steel above and the top of the one below.  On the right, in circles, are the oil hole distance from the hubs lower surface.  The underlined numbers are the steels, again using the hub as the starting point.  Changes are noted in the top of the columns.  Notes on the steels are to the right.

Oil is always moving through the clutch pack.   When engaged the oil is preforming one of its rolls, removing heat.  BMW over the years has reduced the size of the individual friction pads.  This opens the space between pads for oil to flow and carry away heat and debris. 

For some reason I’m not very popular at cocktail parties!

Not sure if the photos came through OK?

https://share.icloud.com/photos/0Az17eYDYWyDvt2odYWa8zx9w

https://share.icloud.com/photos/0X91R8qCvduOBL_TinNYFipIw

[richtea]

First link good, TA.

There's a still image of the matrix, and a movie of it too! (by accident?).

But the second one seems not to be shared correctly. It just says:
'Shared photos not available'

[TA]

I’m using an IPad and have a cloud account.  I historically have a lack of patience with these things.  I read the notice about saving space.  Any additional tips would be helpful. 
Thanks

[Andym535]

Wow. So you're basically stripping the clutch after each ride and assessing the amount of oil on each side of each plate.

Although it's caused by the clutch dragging, the clunk will be coming from the gearbox and I think that's where having thicker oil would be helping to reduce the clunk, as Richard suggests.

I'd agree with Brian that reducing the oil flow to the clutch isn't a good idea.

If you've got a centre stand you might get some measurable value of clutch drag by putting the bike in gear and measuring the force required to turn the back wheel with the clutch pulled in. Not quite sure how you'd do that but I'm sure something could be devised.

[TA]

Andy

Yes, the actual sound is coming from the transmission and drive shaft.  But it is caused by the plates not separating and continuing to spin the whole clutch pack.  I talked to the local BMW dealership service manager.  He has done the Dakar and was on the support team for Ewan Mcgregor and Charley Boorman during Long Way Around.  He said he has know riders who have put o-rings in the transmission to offer some resistance to break the plates.  He was not talking specifically about this K bike.  Breaking the plates is a problem when there is no oil bath to offer resistance or capacity to open the space allowance for the plates. 

Yes, oil flow should be front and centre.  But to backup a bit, these bike have forever have been said to not have enough oil.  I began this exploration with that in mind.  I got nowhere beyond very loud crunches.  When I decided that oil distribution was more promising and began to even this out and reduce the amount of oil, I got glimpses of success.  As far as wear goes, it is the lower hub and the pressure plate that need to be watched.  No problem getting enough oil to the hub.  But as I said, the architecture of the hub makes delivery of oil to the pressure plate difficult.  I would guess that most people find the pressure plate wears sooner than the hub.  Not counting those K12s with that wrongly positioned hole.  As I said, I have upgraded the oil pump. 

I hope I’m not jinxing myself by saying this.  At the moment, for the most part, the clunk is almost gone.  Some noise is good to show the plates are moving loosely and slowly.  I had gotten the plates complete stationary but I couldn’t get into gear without a bit of pressure on the shifter and letting the clutch out until it engaged.  I’m not in a clunk free zone yet.  There is some inconsistency where a clunk appears.   I’m not sure why but have an idea about what could be causing this.  If it is what I suspect, have to live with it.  At the moment I can’t think how it could be dealt with. 

I will try what you suggested about moving the wheel to check the drag. 

Terry

[TA]

Here is a short video from last week.  This is where the plates were stationary and I had to let the clutch out until 1st engaged.  She is fairly quiet, comparatively. 

https://youtu.be/F_BiZiBCbtA

Or go to YouTube and search 2009 K1300R altered clutch.