Seal replacement, clutch plate questions on K25 Camhead

So I split the bike over a three day period of slow, careful work in the garage in order to track down the source of the oil leaking down the back of the motor. Some questions for those of you who have taken this long strange journey:

1. Turns out the leak was coming from the rear main seal, not the counter-balancer seal- bummer. Looks like a bit of a PITA to replace, and the manual is showing two "special tools" for this one . Any advice/tips/tricks on doing that?
2. Bike has 54k miles on it - all mine. Wise advice has been that while you're in there you might as well replace/refresh the clutch. So I measured the OEM friction disk and it came out to 5.9mm. I've read on other posts that new ones measure out to 6.5mm, and the wear limit is 4.4 to 4.6mm, per my Haines manual. So if that be true, by my calculation that clutch disk still has another 100k+ miles left in it, so feeling like changing it out doesn't make sense. Anyone have an opinion that?
3. As for the other major clutch components, I'm thinking that replacing the flywheel cover and clutch spring plate - both spendy items, but also wear items that after 50k might appreciate renewal. Thoughts?

Thanks in advance for any input.

Your clutch plate seems fine. However, if any oil got onto it then I would replace it. They're not that expensive. Why would you replace the spring plate and cover ?? They generally don't wear out. Especially in your case. I've done many clutches for people on tight budgets and only replaced the friction plate. Years later, I've had no negative feedback.

Those seals are replaced by using a self tapping slide hammer. BMW sell the tool for around £50. The DIY route involves you drilling three a small holes (3mm) at 120 degrees to each other in the outer band of the seal and then insert a self tapping scew. Bit at a time, pull the seal out with a claw hammer or pliers. Whatever you have. Pull it out straight though.

Before you pull any seal out it is VERY important that you measure the correct depth of these seals and insert the new ones exactly to that depth.

Having replaced the counter balance seal twice as I put a non OEM seal the first time I recommend you go for a BMW one.

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MotoRevive said:

Your clutch plate seems fine. However, if any oil got onto it then I would replace it. They're not that expensive. Why would you replace the spring plate and cover ?? They generally don't wear out. Especially in your case. I've done many clutches for people on tight budgets and only replaced the friction plate. Years later, I've had no negative feedback.

Those seals are replaced by using a self tapping slide hammer. BMW sell the tool for around £50. The DIY route involves you drilling three a small holes (3mm) at 120 degrees to each other in the outer band of the seal and then insert a self tapping scew. Bit at a time, pull the seal out with a claw hammer or pliers. Whatever you have. Pull it out straight though.

Before you pull any seal out it is VERY important that you measure the correct depth of these seals and insert the new ones exactly to that depth.

Click to expand...

Thanks, MotoR. I heard that the spring plate springs can start to fade with use, making the the clutch engagement looser, which can cause it to slip. So it’s a “while you’re in there” preventative measure.

I’ve also been told that using the current friction disk - which seems to me like it should have a lot of life left in it - with a new cover isn’t a good idea, as the new cover will make the old friction disk wear out faster while the two are mating (terrible turn of phrase there).

Unless I’m wrong on my guesstimate about remaining life in the friction disk, I’m starting to think I should just save the money and only do the seal.

Thanks for the tips on getting it out - very helpful. Any thoughts on how to get the new one in??

waggy said:

Having replaced the counter balance seal twice as I put a non OEM seal the first time I recommend you go for a BMW one.

Click to expand...

Good tip, Waggy - thanks!

I used a 27 mm socket and a tap with a hammer for the balance shaft seal but the other seal is a bit bigger so not sure what would do that

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dirty_t said:

Thanks, MotoR. I heard that the spring plate springs can start to fade with use, making the the clutch engagement looser, which can cause it to slip. So it’s a “while you’re in there” preventative measure.

I’ve also been told that using the current friction disk - which seems to me like it should have a lot of life left in it - with a new cover isn’t a good idea, as the new cover will make the old friction disk wear out faster while the two are mating (terrible turn of phrase there).

Unless I’m wrong on my guesstimate about remaining life in the friction disk, I’m starting to think I should just save the money and only do the seal.

Thanks for the tips on getting it out - very helpful. Any thoughts on how to get the new one in??



Good tip, Waggy - thanks!

Click to expand...

Well of course there is a whole lot of grey area here. If you want to go down the preventative route then why not replace every single part of the bike... I'm being pedantic, but you catch my drift I'm sure.

If all depends on your budget. It is a PITA to get to the clutch but it's far easier the second time (if need be). 54,000 miles on a clutch is NOTHING unless you ride like a loon or have contamination. I've known clutches that have lasted 200,000 miles +.

When I worked for a main dealer, we would change these seals quite often under warranty and never change the clutch plate. You don't just swap parts because you can see them. Especially if they are well within tolerance.

Also, the clutch friction plate and the cover are NOT paired for life. In a perfect world where cost is no issue you could swap both together, but I personally don't see the need nor have a ever been instructed by BMW technical to do so. You don't change your brake discs every time your pads wear out do you. BMW don't even state a wear limit for the cover. Only it's lateral runout. Basically, if it moves side to side. They only say to replace it if there is signs of scoring or uneven wear.. So if it looks good, leave it alone.

Clutches are pretty much self centring too. I've copied some specs for you below.


21 21 - Clutch with driver plate

Diameter of clutch plate
180 mm


Clutch plate thickness
Wear limit; measured pressed together at rivets of clutch plate
4.4...4.6 mm


Distortion of driver plate
Lateral runout
max 0.1 mm


Distortion of thrust plate and housing cover
0.1...0.2 mm


As for fitting the new seals, use a large socket that is JUST smaller than the seal outer diameter. If you get stuck in this respect, measure the seal with some Vernier Calipers and then order some Aluminium or nylon round tube which is a touch smaller. You can buy it pretty cheaply on Ebay. It is IMPERATIVE that you install the seal straight. And carefully. Tapping it in 'pissed' will ruin the seal

Meticulously clean the the shaft and the engine casing with brake cleaner before you install it. DO NOT LUBRICATE THE SEAL before installation.

Good luck...

MotoRevive said:

You don't change your brake discs every time your pads wear out do you?...

Click to expand...

Sorry, but with BMW main dealers, (car or bike) you damn nearly do!

Took the subframe off mine to get it powder coated as it was a tad corroded... as it was only a few more bolts I thought I would take the gearbox off to get to the clutch... bottom dowel was a tad corroded.... but box came off with a bit of heat and persuasion . My bike has also done similar mileage to yours and clutch plate had same wear . As I intend to keep the bike till I am too old and decrepit to ride it , I replaced the plate ... while i was in there .

Shaft seal showed no sign of leak so left alone ..

I have always been a ‘while I am there I will replace stuff’.

And when I say ‘a tad corroded’.....it was rusty as fek!!!!!

Myke Rocks said:

Sorry, but with BMW main dealers, (car or bike) you damn nearly do!

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HAHAH. I know right. BMW tell you that your discs are worn when there is 0.5mm worn off them. It's a complete scam. Part of the BMW service is measuring the discs. So they HAVE to tell you that they're worn out if BMW tell you they're below their limit and tell you to replace them. And you've seen the cost.

Those same discs will pass an MOT for the next ten years.

dirty_t said:

So I split the bike over a three day period of slow, careful work in the garage in order to track down the source of the oil leaking down the back of the motor. Some questions for those of you who have taken this long strange journey:


Turns out the leak was coming from the rear main seal, not the counter-balancer seal- bummer. Looks like a bit of a PITA to replace, and the manual is showing two "special tools" for this one . Any advice/tips/tricks on doing that?
Thanks in advance for any input.

Click to expand...

There are two types of crankshaft seals available:-
1. the standard type with compression spring.
And
2. Teflon seal.

It is possible to fit the standard seal conventionally using something to tap it home, I used the oil filter removal tool which has the same diameter.

The Teflon seal is a bit more involved. It requires the sealing lip to be stretched slightly to fit over the crank shaft, this is the reason for the special tools. The seal must also be installed dry.

There is a machined shelf in the casing so no need to worry about measuring depth, as the seal can’t go in further than the shelf. Tap home until it bottoms out.

Good luck
Ian

MotoRevive said:

If all depends on your budget. It is a PITA to get to the clutch but it's far easier the second time (if need be). 54,000 miles on a clutch is NOTHING unless you ride like a loon or have contamination. I've known clutches that have lasted 200,000 miles +.
Also, the clutch friction plate and the cover are NOT paired for life. In a perfect world where cost is no issue you could swap both together, but I personally don't see the need nor have a ever been instructed by BMW technical to do so. You don't change your brake discs every time your pads wear out do you. BMW don't even state a wear limit for the cover. Only it's lateral runout. Basically, if it moves side to side. They only say to replace it if there is signs of scoring or uneven wear.. So if it looks good, leave it alone.

Clutches are pretty much self centring too. I've copied some specs for you below.


21 21 - Clutch with driver plate

Diameter of clutch plate
180 mm


Clutch plate thickness
Wear limit; measured pressed together at rivets of clutch plate
4.4...4.6 mm


Distortion of driver plate
Lateral runout
max 0.1 mm


Distortion of thrust plate and housing cover
0.1...0.2 mm


As for fitting the new seals, use a large socket that is JUST smaller than the seal outer diameter. If you get stuck in this respect, measure the seal with some Vernier Calipers and then order some Aluminium or nylon round tube which is a touch smaller. You can buy it pretty cheaply on Ebay. It is IMPERATIVE that you install the seal straight. And carefully. Tapping it in 'pissed' will ruin the seal

Meticulously clean the the shaft and the engine casing with brake cleaner before you install it. DO NOT LUBRICATE THE SEAL before installation.

Good luck...

Click to expand...

Great info, MotoRevive - thank you! (Sounds like you repair bikes for your day job, yes?)

Ian J Hartley said:

There are two types of crankshaft seals available:-
1. the standard type with compression spring.
And
2. Teflon seal.

It is possible to fit the standard seal conventionally using something to tap it home, I used the oil filter removal tool which has the same diameter.

The Teflon seal is a bit more involved. It requires the sealing lip to be stretched slightly to fit over the crank shaft, this is the reason for the special tools. The seal must also be installed dry.

There is a machined shelf in the casing so no need to worry about measuring depth, as the seal can’t go in further than the shelf. Tap home until it bottoms out.

Good luck
Ian

Click to expand...

Thanks, Ian - very helpful. Yeah, I read about the two different types of seal in the Haines manual - they even had a pictures of both to help you identify which one you’ve got, because one should be lubricated, and the other, not.

As for the special tools, I’m hoping I can gerryrig something up for them, or maybe find someone here in the US to borrow them from. Or maybe even see if I can 3D print a set of them. that would be kinda fun, actually.

dirty_t said:

Great info, MotoRevive - thank you! (Sounds like you repair bikes for your day job, yes?)

Click to expand...

Yes. I run an independent workshop on the Wirral. Specialising in BMWs.

I was working for a main dealer as a Tech for the last eight years, as well as for myself at home on the older models.

Depends if you use the bike daily as the only transport, if that’s the case I would replace the whole clutch while the bike is split , although you say the wear is fine I’ve seen friction material delaminate over time. Depends if you’ve got the time to split the back end later if needed.


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Changing the clutch on an R1150GS is a right pain in the arse. But breaking the R1200GS twin cam to get to the clutch is a doddle in comparison. I have had to do it twice on my bike to change the original crank shaft oil seal at 18946 miles, and again at 24444 miles, presumably because either the seal I fitted was faulty, or I screwed up the fitment. I removed and refitted all the clutch components, just replacing the 5 stress bolts holding the clutch assembly to the crankshaft.

Anyway, my point is that because the bike is easy to split to get to the clutch, then I would have no hesitation in letting the clutch go to the limit.

Ian

Ian J Hartley said:

There are two types of crankshaft seals available:-
1. the standard type with compression spring.
And
2. Teflon seal.

It is possible to fit the standard seal conventionally using something to tap it home, I used the oil filter removal tool which has the same diameter.

The Teflon seal is a bit more involved. It requires the sealing lip to be stretched slightly to fit over the crank shaft, this is the reason for the special tools. The seal must also be installed dry.

There is a machined shelf in the casing so no need to worry about measuring depth, as the seal can’t go in further than the shelf. Tap home until it bottoms out.

Good luck
Ian

Click to expand...

I have change by myself two clutch discs but only discs

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Ian J Hartley said:

Changing the clutch on an R1150GS is a right pain in the arse. But breaking the R1200GS twin cam to get to the clutch is a doddle in comparison. I have had to do it twice on my bike to change the original crank shaft oil seal at 18946 miles, and again at 24444 miles, presumably because either the seal I fitted was faulty, or I screwed up the fitment. I removed and refitted all the clutch components, just replacing the 5 stress bolts holding the clutch assembly to the crankshaft.

Anyway, my point is that because the bike is easy to split to get to the clutch, then I would have no hesitation in letting the clutch go to the limit.

Ian

Click to expand...

Interesting perspective. I've been struggling getting the dang thing joined back together again. I think it's down to losing the rear of the drive shaft, which is not blocking the two frame halves from coming together. Spent a couple hours wrestling the SOB with my wife on one end or the other to help, and getting nowhere.

Next up - dropping the rear swingarm pivot, re-seating the drive shaft there, and hopefully - finally - getting the thing bolted back together again. Been a process - but the learning curve is steep, so if I have to do this again should go considerably faster.

I treated the drive shaft as a separate issue. Bolted the bike back together first, and then took off the rear wheel and hinged down the final drive to sort out the drive shaft.

It’s easy levering the drive shaft off the spline snap ring, but I found getting it back near impossible to lever back on. It required a whack with the hammer from the final drive end.

Ian