How to determine wear condition of clutch parts

[Motorhobo]

First -- I would love to a brand new OEM clutch pack but it's not going to happen. So -- I have two clutch packs pulled from my bikes to choose from and am trying to determine which is in better condition. Tolerance for the friction disk is pretty well documented so I'm OK with that. I have a new clutch ring lying around, so that's good. But I haven't found any way to determine what the wear condition is of the rest of the parts, i.e. diaphragm spring, pressure plate and housing cover (3,4, and 6 on diagram).

The clutch splines fried on one of my bikes recently. The disk had probably at least 30k on it. The last time I pulled it was probably around 15k ago and it looked OK then. Could the failure or excessive wear of any of 3,4, or 6 have caused those splines to fail?

Are there any specs or more info to help determine the wear condition of 3,4, and 6? These parts are all metal don't appear to have any high-wear surfaces.

Thanks for any info...

MH

[kennybobby]

Grease...is the word.  Lack thereof is the root cause of spline failure.

[Motorhobo]

They were lubed with Guard Dog 15k miles ago which is within the maintenance window. That's why I'm thinking there might have been something else going on and am asking about the how to determine wear on the other parts, and whether wear on the other clutch parts can result in clutch disk seizure and spline failure.

[Motorhobo]

Forgot the diagram -- here it is.

[kennybobby]

Did you use the paste or the grease from guard dog? 

Was there any left on the splines of either the shaft or the spring plate when you opened it up?

Powdered Moly can be a good lubricant but the base carrier is important too.  The oem red grease is very tacky with lots of sticking power--maybe mix some moly in with the red

[Motorhobo]

The paste -- recommended product here on Motobrick for K-Bike splines.

http://www.motobrick.com/index.php/topic,663.msg1982.html#msg1982

The question is whether other factors having to do with the wear condition of other clutch parts or clutch balance can contribute to clutch disk spline failure. I'm not concerned with the lube question. Let's just assume they were adequately lubed, which they were. I'm interested in other possible factors.

[Laitch]

That's why I'm thinking there might have been something else going on and am asking about the how to determine wear on the other parts, and whether wear on the other clutch parts can result in clutch disk seizure and spline failure.

Misalignment of the clutch disc in the housing before it's completely tightened down could result in damaged disc splines. I use an alignment tool and a painfully obsessive test-as-I-tighten-the-clutch-bolts ritual. Others who align tool-lessly may have a magical touch or a visual acuity that my genes missed leaving the pool. Chris Harris shows an abbreviated and more confident version of the test in his K100 spline lube video while replacing the clutch pack.

[Motorhobo]

I have one of Ken Lively's tools and thought I had it right. In retrospect maybe there was more vibration thAn o should have expected.

So 3,4 and 6 are forever parts? Is there a recommended replacement interval?

[Laitch]

I have one of Ken Lively's tools and thought I had it right. In retrospect maybe there was more vibration thAn o should have expected.

So 3,4 and 6 are forever parts? Is there a recommended replacement interval?

Depending upon the demand on the clutch, 2, 3 and 4 are items subject to fatigue. Replacement intervals don't seem to be promoted by BMW, and they never miss a chance to encourage spending. Balance of the clutch pack is promoted as critical to vibration-free operation. Missing dowel locators in the housing also can result in misalignment and spline failure.

[Quiltzig]

I have one of Ken Lively's tools and thought I had it right. In retrospect maybe there was more vibration thAn o should have expected.

So 3,4 and 6 are forever parts? Is there a recommended replacement interval?

Vibration is an indicator of out of balance clutch parts. I got my carrier, disc, pressure plate, etc dynamically balanced as a set, and the difference in smoothness and ease of gear changes was instantly and massively apparent. I would suggest alignment is 70% of the issue, balance is the other factor.

Apart from a very weak pressure plate, which would be evident as clutch drag, the plate is what wears, not the metal parts as a rule.

[Motorhobo]

Vibration is an indicator of out of balance clutch parts. I got my carrier, disc, pressure plate, etc dynamically balanced as a set, and the difference in smoothness and ease of gear changes was instantly and massively apparent. I would suggest alignment is 70% of the issue, balance is the other factor.

Apart from a very weak pressure plate, which would be evident as clutch drag, the plate is what wears, not the metal parts as a rule.

That's exactly the kind of information I'm looking for. Can you describe 'clutch drag' a bit more in detail?

There are a couple threads here about clutch alignment and all of them reference 'marks' on the parts that are visible when the parts ship from the factory but perhaps not visible after a period of use for whatever reason.  But what all clutch parts have in common, regardless of whether these alignment marks are visible or not, are part designations stamped into the metal. When I disassembled the clutch of the donor K75 I'm tearing down I took detailed photos of the existing marks and the orientation of the parts as assembled, including the part stamps. This bike rode smooth -- no vibration -- so I can assume the alignment was properly done.  Shouldn't it be possible, based on these part stamps, to determine the correct alignment even if the marks aren't visible? The stamps are permanent -- the marks aren't. Using the stamps as alignment reference should be a reliable method in situations where no marks are visible.

Or am I missing something here? 

[Quiltzig]

The factory puts some paint marks on the parts when they assemble them. They are relatively balanced but not dynamically so.
The ones that I have taken apart have not had visible marks, but I marked them so I could replicate the orientation on reassembly.

On one bike, a K1200 RS that I fitted a new motor into, I had a choice of the old clutch carrier or the new one, and as it was going to be a mixture, I opted to have the entire clutch assembly balanced. This bike now has the slickest gear change of any BMW that I have owned. It is incredibly slick.

By a dragging clutch I means one where you continue to move forwards if the clutch is fully pulled in whilst in gear. It is pretty rare... which is why I don't think this is your problem.

I use Guard Dog moly on all my clutch splines, and have not had an issue with any of the 5 bikes that I maintain. It cost me NZ $60 to balance the parts, and the guy who did it commented that the parts were quite well out of balance, so even from the factory they are not 100%. I think Chris Harris has commented on this in the past as well.

[Motorhobo]

This is awesome info Quilty -- thanks.

By a dragging clutch I means one where you continue to move forwards if the clutch is fully pulled in whilst in gear. It is pretty rare... which is why I don't think this is your problem.

I have something similar -- when engine-braking to a stop and pulling in the clutch to brake the last few mph before the full stop, it would feel like the clutch is still at least partially engaged even though the clutch lever was fully in. So the bike would continue to engine-brake rather than freewheel with the clutch pulled in. A little blib of the throttle would cause it to fully disengage to freewheel. But a condition you described, where the bike would move forward with the clutch fully pulled, in did not occur. At the time I speculated that it was possibly a weak diaphragm spring that was causing this symptom -- but noone responded so...well, I just assumed it wasn't something I needed to worry too much about.

Not sure what you mean about relatively and dynamically balanced.

My contention is that if there are marks applied to the individual clutch parts in a balanced assembly, it should be possible to reproduce that balanced configuration based on the stamps in the metal. The stamps will be the in the same position for every single part produced, just as the weight distribution is the same for every part produced. Let me see if I can put together an animation to demonstrate what I mean. In the meantime, I will use the clutch pack that from the tear-down bike -- that one didn't have that draggy thing I described above so the parts are probably in better condition, and I marked them on disassembly.

[kennybobby]

The excessive vibration and the dragging clutch during engine braking should have been mentioned in the original post since you are trying to fix several issues and not just swapping out parts due to normal or advance spline wear.

The dragging clutch problem could an indication of too much stretch or slack in the adjustment of the clutch cable, which can lead to chattering on the splines.

The excessive vibration is a mass-imbalance issue.  The heavy spots on the 3 big heavy pieces (housing, pp, cover plate) are marked and then assembled with 120 degree spacing between them to try to reduce the overall imbalance. 

An unknown factor during assembly is the position of the counterbalance weights on the output shaft inside the engine and how that interacts with the clutch pack residual imbalance--figure that out and you will be crowned kkk, the kbike klutch king

[Motorhobo]

The dragging clutch problem could be a symptom of failing pushrod splines, or an indication of too much stretch or slack in the adjustment of the clutch cable, which can also lead to failing splines.

Pushrod splines -- that's a new one on me. Search of site found references only to 'clutch pushrod' so can you please elaborate on which splines you're referring to here?

It was probably clutch cable adjustment, in retrospect.

The excessive vibration is a mass-imbalance issue.  The heavy spots on the 3 big heavy pieces (housing, pp, cover plate) are marked and then assembled with 120 degree spacing between them to try to reduce the overall imbalance. 

Shouldn't it be possible to identify these heavy spots based on their position relative to the stamps on the metal of the respective part?

An unknown factor during assembly is the position of the counterbalance weights on the output shaft inside the engine and how that interacts with the clutch pack residual imbalance--figure that out and you will be crowned kkk, the kbike klutch king

I'd be more than satisfied to come up with a way to balance the clutch parts without relying on some indeterminate 'mark' that may or may be present.

Thanks for this info -- let me think on it for a couple days -- can't reinstall the clutch anyway right now because I'm waiting for clutch washers to get here.

[kennybobby]

Sorry i was in spline fog due to lack of coffee...corrected it

The heavy parts are made from castings, which have a larger degree of variability than a part machined from a solid billet.  The castings get machined to add the nice flats and mounting holes, etc. but each one is different and needs it's own balancing.  For sure, the stamping marks could be used as a fixed reference rather than the paint marks once the balancing is known, e.g. heavy spot is xxx degrees CW from the stamping.

Do you have a wheel balancing stand--with a custom adapter it could be used to balance all the parts bolted up together.   i've made them for ducati and bmw rear wheels, maybe should look into making one for this.

[Quiltzig]

This is awesome info Quilty -- thanks.

Not sure what you mean about relatively and dynamically balanced.

My contention is that if there are marks applied to the individual clutch parts in a balanced assembly, it should be possible to reproduce that balanced configuration based on the stamps in the metal. The stamps will be the in the same position for every single part produced, just as the weight distribution is the same for every part produced. Let me see if I can put together an animation to demonstrate what I mean. In the meantime, I will use the clutch pack that from the tear-down bike -- that one didn't have that draggy thing I described above so the parts are probably in better condition, and I marked them on disassembly.

Even when aligned to the factory marks the whole assembly is not balanced whilst spinning. It is a static balance situation. When you do a dynamic balance you take the whole assembly and spin it in a machine which then computes where and how much imbalance there it. They then drill holes at the heaviest part (I wish I had taken before and after pics of this) - but basically it was 5 or six holes about 8mm dia and 5 or 6mm deep that were drilled to lighten an area of the clutch carrier. They guy showed me in his machine how much out of balance it was before and reckoned that afterwards it was totally in balance. Certainly I can feel it. I have two almost identical K1200RS bikes, and this one is super smooth. The company that I used does balancing of all sorts of car parts, mainly driveshafts.