93 K75 clutch splines GONE!

[rrmullerr]

Hi all,
first time post on here, apologies if i'm doing things wrong, just let me know i'm happy to correct.
i've learned a lot from lurking on here and now i've got an issue of my own to resolve.

a little history:
i picked up a '93 K75 about 2.5 years ago and i've quickly fallen in love with it.  it's been my daily commuter into NYC, year-round, and has been both a workhorse and fun!  About 1.5 yrs ago the shifting was getting a little clunky.  since i have two kids under 3 and a 90 year old house i reluctantly brought it into a well recommended shop to have the splines lubed all the way back to the clutch.  It seemed better and was it's typical reliable self until last week...  on the west side highway i shifted into 5th and just got a loud whine/whir and loss of power.  fortunately i was able to coast off at the next exit and get a tow home.  Eventually i found some late-night hours to open it up, praying for only a final drive issue, i kept tearing back until i found my clutch disc splines completely obliterated!  and the input shaft chewed up too.  what a bummer!

this is where i could use some of the expert help on here:  my current plan was to just get a used gearbox, since that seems like the most economical resolution.  I didn't see anything on the boneyard or kbikeparts, but there were some on ebay which seem ok (although i'm scared of just trusting pics and postmen).  I'm also in the market for a clutch disc, although once i inspect further i'm thinking it might be wise to just get the whole pack.  The clutch nut was dry, but the boot i'll replace, anything else i should be worried about?

Here's some pics, i think it all looks ok until you get to the end :(

Final drive:


shaft out:


shaft in:


transmission out:


transmission input and clutch 



thanks for any input, it's my first time this deep into the bike and it'll be great to get advice or at least reassurance to keep going.
Ryan

[Laitch]

If you can afford to replace the entire clutch pack, have at it but it's probably only the clutch disc that is damaged. We need a straight-on shot of the input splines of the transmission. The plan of transmission replacement is typical when a transmission's input splines are shot. That would depend upon whether you have the time, tools and patience to disassemble the transmission.

Does the intermediate housing or transmission have a couple of locating dowels (at red arrows) installed in one or the other? Absence of them is one cause of clutch hub wear because of misalingment.

[The Mighty Gryphon]

Your driveshaft and final drive should be good for another 100,000 miles.

Pretty much any K100 or K75 transmission will work.  Most of the dealers on eBay sell good stuff so I'd go with them instead of a private seller. 

There are some sources for reasonably priced clutch plates, maybe someone will suggest one.  I've heard that a VW clutch can work, but I have no actual experience going that route.  If you find a transmission, possibly you can get a low miles clutch along with it.

[frankenduck]

Does the intermediate housing or transmission have a couple of locating dowels (at red arrows) installed in one or the other? Absence of them is one cause of clutch hub wear because of misalingment.

They all do. The urban legend regarding bellhousing misalignment is that some early ones weren't uncrated properly at some dealers and that that is what caused some misalignment.  You can also supposedly DIY it by highcentering the bike or, of couse, getting T-boned by a car.

The usual symptom of dry clutch splines is getting false neutrals on downshifts like 4>3 or 3>2 riding into a turn.

[The Mighty Gryphon]

I've bought a number of parts from this dealer over the years.  His stuff is reasonably priced and in good working condition.  Right now he has two K75 transmissions for sale.

https://www.ebay.com/itm/333958339513?hash=item4dc177dbb9:g:6mQAAOSwaz9gdgBD

https://www.ebay.com/itm/353405830260?hash=item5248a10474:g:7LkAAOSwOo5fpc3y

Here are the clutch packs that were on the bikes with the transmissions:

https://www.ebay.com/itm/353455625857?hash=item524b98d681:g:a-UAAOSwB65gdgK3

https://www.ebay.com/itm/353437619111?hash=item524a8613a7:g:UVoAAOSweRBfJJwK

He's pretty good about answering questions and getting additional photos if you need to see a detail.

[frankenduck]

You probably want to get a 1990 or later transmission. I would.  BMW hardened the input splines in 1990 and the spline lube interval went from annual to 40K.

[rrmullerr]

Thanks to you all!  and thanks for your patience with my slow responses

Laitch,
here's an image of the housing, dowels attached, although in different location that yours. 


and here's more pics of the input splines:



Gryphon,
Thanks for the links, there are some others on ebay from newer bikes, any of you worked with TheMotoGuys based in Anaheim?  i also have a promising lead on another that's a more reliable source.
Also very glad to hear that the rest of the spines are good to your experienced eyes as well.

Thanks also Duck,
weirdly i was not getting any false neutrals, and really very minimal sticking around 2nd gear, but nothing that made me think they were as bad as they are... its almost like the sheared all at once.

I was just visiting with my folks and there was a cherry 91 K75S in the town over for a great deal... so that is my temporary fix!  haha.  but i love this one too and can't wait to get it back up and on the road soon.

[CTDOM!]

You know while you are there you should change the seals on the main shaft. The o-ring and main seal are right there now that you have it all open, it would be insult to injury to put it all back together and have them let go splattering your new clutch with oil.

I bought the disc three years ago now from Wunderlich: Part number 2122795 for $249.95. I also bought the alignment tool since I like tools and for 23 bucks I figured it would save me some sort of time. Haven't had to look to see if someone had it or cheaper.

Your spline looks fine, I don't see anything that would make me swap the transmission. I'll let other weigh in though.

[frankenduck]

You know while you are there you should change the seals on the main shaft. The o-ring and main seal are right there now that you have it all open, it would be insult to injury to put it all back together and have them let go splattering your new clutch with oil.

I bought the disc three years ago now from Wunderlich: Part number 2122795 for $249.95. I also bought the alignment tool since I like tools and for 23 bucks I figured it would save me some sort of time. Haven't had to look to see if someone had it or cheaper.

Your spline looks fine, I don't see anything that would make me swap the transmission. I'll let other weigh in though.

Unless you plug the weep hole and form a puddle of oil in the bottom of the bellhousing there's no way a leaky main seal will foul a clutch.  Even with a bad O-ring you'd have to put in a lot of miles for any oil to get to the clutch friction surface.  I bought a used bike with a bad O-ring. Put about 3,000 miles on it before replacing the O-ring and not a drop of oil got on the clutch.  It just spins out the side of the clutch basket.

[CTDOM!]

Mine was slipping like mad when I got it and sort of had a few drips out the weep hole. So I had to do mine.

My disc was pretty nasty with oil, your are lucky and I am not I guess.   It's done now the miles keep adding up now.

If it were me, I would do it since it is cheap insurance since the bike is so far disassembled.

[The Mighty Gryphon]

I'm inclined to think those input splines don't look too bad.  I suspect the splines on the clutch are softer so they don't tear up the input shaft. Being the crotchety, cheap bastard I am, I would give the old splines a chance. 

Look at the top of the splines, if there is a nice wide flat area that is even width for the full length, I would think they're still usable.

[rrmullerr]

well now that i have the second bike i'm more inclined to try that.  i commute daily on the bike.

The splines look ok at the end, but then 3/4" down they look pretty chewed up, it's clear in the picture from my original post.  is that a wear pattern you've seen before?

if i can find a good replacement i'll jump on it, but if not maybe this has some life.

as for the o-ring - it's dry, and i'm inclined to the 'if it aint broke dont fix it' school of thought, but i'm also being swayed by my lack of a 30mm socket on hand. 
It was also much easier to get this far back into the bike than i thought, so as long as it doesn't strand me somewhere i'm not so concerned to have to open it up again.

Thanks again to you all for such great insight.

[CTDOM!]

Clean the splines up and then see what they look like.  Hard for me to really tell in the earlier picture since it just looks like old grease.

[The Mighty Gryphon]

I would at least change the o-ring.  As long as you have the clutch basket off it's fairly easy and a new Viton one is a couple bucks at any local bearing supplier.  If the seal isn't showing signs of leaking I'd leave it alone, but the o-ring is almost sure to be hard and destined to leak in the not distant future.

[Laitch]

Does the intermediate housing or transmission have a couple of locating dowels (at red arrows) installed in one or the other?

They all do. The urban legend regarding bellhousing misalignment is that some early ones weren't uncrated properly at some dealers and that that is what caused some misalignment.

Apparently, they all don't as evidenced by the attached extract from BMW cautionary service bulletin #2232 entitled Clutch Spline Failure–K models. Consider putting it on your reading list for the next contagion.    t's not so much urban legend at the root but rather occasional assembly inattention that causes this.

[Motorhobo]

Sachs aftermarket clutch parts through tills.de:

https://www.tills.de/bmw-k75-67/clutch-69/

IMO that's an awesome price for the clutch bolts which need to be replaced every install, I don't know if there's any comparable price anywhere even with the shipping from EU.

BTW I blew out my clutch plate once by misaligning the clutch parts on installation. I knew it was wrong as soon as I rode the bike -- excess vibration. I rode it anyway and after maybe a thousand miles...  splines gone, no power. Fortunately, about 1/2 mile from home. Pushing K75 1/2 mile -- no fun, had sore calves for days.