Clutch and oil

[TA]

Does a wet clutch need oil delivered while disengaged? 

[black-k1]

My answer would be yes otherwise a long run without it being engaged (motorway) would result in it eventually being used when it's a not-very-wet-at-all clutch.

[chriscanning]

You can arrive at the answer yes just by studying the K history,when I bought my K Sport in 09 the oil spec was 10/40 because of all the drama that BM had with said K clutch’s they eventually went to 5/40.

I remember being in Vines when they asked what spec oil did I want and quickly reminded that they were the experts not me so went 5/40 very early on in the process.

The first time Vines attempted to fix the classic clutch take up right at the end of the lever it lasted 6 weeks before it resorted to how it used to be,their second attempt has worked to this day sadly I do not know what they did.

For some reason from the very first days of the net anything tech I have printed off and keep’d in a file,years back I had a Dutch guy contact me about and clutch updates and I managed to get hold of a factory circular to dealers which frankly was frightening as they were expecting them to drill a hole in the end of the clutch shaft to improve circulation,it came with photos and I lost the dam thing and then changed computers,I think it was for the pre 07 K’s but was never certain of that.

Guess I could have said yes too the question......oh hang on I did..

[Costas]

Take a look, in this .
https://documentcloud.adobe.com/link/review?uri=urn%3Aaaid%3Ascds%3AUS%3A7bf610f9-08e4-43d7-80f2-b9562851f52c

[TA]

Costas

I think I’ve missed what was in that article about oil and non-engagement.   

Here is what I found to be a digestible paper on oil and wet clutches.  It does not directly talk of oil during non-engagement.  But it does talk about static and dynamic friction and the transition between them, one of oils main functions.

syntheticwarehouse.com

[Phmode]

Being in a picky, spikey sort of mood this morning (caused by the Pink Moon over the pub at 03:25 this morning) we seem to have different understandings of when a clutch is engaged and when it is disengaged.

The original question was whether the clutch needed oil delivered while disengaged. I take disengaged to mean lever pulled in, engine side of clutch not connected to gearbox side of clutch.

David's answer seems to suggest it is disengaged while on a long motorway run 

The technical answer, according to TomL is that oil only gets fed to the clutch plates whilst the clutch is disengaged i.e. lever pulled in.

That's why lots of us sit with the lever pulled in at lights etc. so giving the plates a good soak.

I have no idea why wet clutches are even used. Cars, even multi-plate competition cars work perfectly well with no lube, in fact just the opposite. Even a few tiny drops of oil on a car clutch can cause it to slip like buggery.

I remember asking my dad (who knew everything) why it had oil in there when I was told to lap in the new cork inserts on the clutch plates of some bike or other when I were a lad.

'It just has!' So that was one thing he didn't know then...

[TomL]

Apparently the oil washes the clutch friction dust off the plates. Poor oil flow across the plates allows the clutch plate dust to form into a paste on the clutch plates.

Downside is that it washes it into the engine oil which is why engine oil gets contaminate so quickly and it has to be changed more frequently than in cars.

The trick is to sit at lights and junctions with the clutch pulled in to clean the plates. Formerly I would always put my bike into neutral.

[Phmode]

You can still have the bike in neutral with the lever pulled, the clutch knows no difference, apart from maybe a little less drag.

As to the paste, the dust can only turn into a paste if there is a liquid such as oil in there to emulify it, otherwise, just like in a car, it is merely dry dust.

I realise that there is oil there on the K, but the question remains, 'Why?'.

[TA]

Here is part of a patent about controlling the amount of oil at different clutch stages.  It is addressing the need for a low oil flow during disengagement.   A higher oil flow during disengagement causes clutch drag = klunk.  Oils important function is during the process of engagement and disengagement.  Outside of those two states, oils function is nominal. 

Type in search - oil modulation clutch patent  -  it should be the first listing under data.epo.org

Sorry, I couldn’t get a direct address.

[TA]

Having watched 404 and Patric H videos, the debris within the clutch is mostly generated at the hub and pressure plate.  Everywhere else within the plate stack, the plates look relatively unaffected whether little or lots of oil   So to me that says at those two surfaces is where a good oil flow is needed.

[Phmode]

None of this explains why bike clutches use oil when car clutches don't 

[TA]

The little bit I’ve come across is a wet clutch last longer.   Contributing to that is the cooling offered by the oil. 

[TA]

I found this.  If your question is not rhetorical.

To kick things off lets talk about wet clutches. They're referred to as wet because they're bathed in engine oil. The oil's primary purpose is to cool the clutch plates, and because of this cooling effect wet clutches can take a lot of abuse, like the kind you'd dish out in stop and go traffic. Wet clutches generally have a nice wide friction zone that makes them pretty easy to use. They also tend to last a long time, and they're quieter than dry clutches. And did we mention that they can take a lot of abuse? That's a good characteristic, especially if you're just learning how to ride or don't want to replace your motorcycle clutch every 10,000 miles.

On the flip side, wet clutches do make your engine oil dirty faster since all the dust that's created as the clutch wears stays inside the engine. Thankfully, the oil filter takes care of that. The other drawback is that wet clutches are messier to work on. Also, because the clutch is spinning in oil, there's fluid drag that saps a bit of the engine's power.

[black-k1]

Being in a picky, spikey sort of mood this morning (caused by the Pink Moon over the pub at 03:25 this morning) we seem to have different understandings of when a clutch is engaged and when it is disengaged.

The original question was whether the clutch needed oil delivered while disengaged. I take disengaged to mean lever pulled in, engine side of clutch not connected to gearbox side of clutch.

David's answer seems to suggest it is disengaged while on a long motorway run 

The technical answer, according to TomL is that oil only gets fed to the clutch plates whilst the clutch is disengaged i.e. lever pulled in.

That's why lots of us sit with the lever pulled in at lights etc. so giving the plates a good soak.

I have no idea why wet clutches are even used. Cars, even multi-plate competition cars work perfectly well with no lube, in fact just the opposite. Even a few tiny drops of oil on a car clutch can cause it to slip like buggery.

I remember asking my dad (who knew everything) why it had oil in there when I was told to lap in the new cork inserts on the clutch plates of some bike or other when I were a lad.

'It just has!' So that was one thing he didn't know then...

You are quite right Brian, while the post said disengaged, I read engaged.

[Phmode]

I found this.  If your question is not rhetorical.

To kick things off lets talk about wet clutches. They're referred to as wet because they're bathed in engine oil. The oil's primary purpose is to cool the clutch plates, and because of this cooling effect wet clutches can take a lot of abuse, like the kind you'd dish out in stop and go traffic. Wet clutches generally have a nice wide friction zone that makes them pretty easy to use. They also tend to last a long time, and they're quieter than dry clutches. And did we mention that they can take a lot of abuse? That's a good characteristic, especially if you're just learning how to ride or don't want to replace your motorcycle clutch every 10,000 miles.

On the flip side, wet clutches do make your engine oil dirty faster since all the dust that's created as the clutch wears stays inside the engine. Thankfully, the oil filter takes care of that. The other drawback is that wet clutches are messier to work on. Also, because the clutch is spinning in oil, there's fluid drag that saps a bit of the engine's power.

Thanks and the question was not rhetorical. Pointless perhaps, but not rhetorical.

And I do get all of that. My point remains that all of the above pro's would apply to a car, van, truck clutch also. But almost (get your exclusion clauses in early I say) no car, van or truck uses a wet clutch.

Believe me, the clutch in my S3 (and every other car I have ever owned) gets used and sensibly abused every bit as much as my K13 or tiny Honda ones.

The only differences I can think of are that bike clutches are, for a given size of engine and power output, small in diameter compared with car clutches. They make up for that size deficiency by using multiple plates whereas (almost) all cars use a single plate clutch. Really high performance cars tend to use twin plate clutches.

Most bikes carry their engines lower than most cars and so a large diameter clutch housing may get in the way of the ground...

Someone must know why. Not the advantages, because cars need those advantages also.