K75 weepage: gear or motor oil?

[stryder]

Hi there,

as usual, every year at ther start of the new riding season I check the weep hole under the gear box for drips and signs of a main rear seal on the way out like a well informed K75-er should when putting the bike on the road after 6 months storage. Much to my dismay, for the first time ever, I see signs of weepage from the inside as I wiped down the tranny and engine to eliminate seepage from a cracked boot or loose oil pan etc. Sure enough, it's coming from the inside, tell tale weepage on right side bell gear box housing/engine joint too.

So, I pull every thing apart, due for a clutch spline lube anyway, and it looks more like a gear oil leak than a motor oil leak. Also, yesterday, I noticed some clear oil had gathered around the weep hole after a thorough wipe down so I figure if it was motor oil it'd be dark. I wipe down the insides of the engine bell housing and gear box housing interiors and let them sit for 4 hours, the gear box canted forward, and the engine for sure has enough oil in it but, I can't see any signs of weepage from the rear main seal/clutch o-ring re motor oil , i.e. a trail of oil from those areas down to the housing,  or from the gear box seal around the input shaft. Checked the torque on the gear box hex bolts on the perimeter of the gear box cover and none could be budged. There does seem to have been some weepage around that gasket though.

Any comments or feedback on why the leaking/weeping "disappeared? Should I let them sit overnight? 

I'd hate to put everything back together just to have it start weeping again.

Thanks.

[Scott_]

So, if you are at the position of having it all open and exposed, why not just bite the bullet and replace both seals, engine rear main and trans input shaft, and the clutch nut o-ring, and be done with it...........

[stryder]

I hear what you're saying but:

1) I suffer from cheapbastarditus;

2) I strongly believe that if it ain't broke it shouldn't be fixed. (maybe 80, 000 miles on hers and those seals usually go around 120K mile IIRC)

:)

If only I can get either or to leak and show me what needs to be replaced.

How else would gear oil get in there if not for a input shaft seal? 

If the rear main or clutch o-ring were the culprits, one would think after 4 hours I'd see something. 

[TimTyler]

My rear main seal was leaking when I bought the bike @ 80k miles. I replaced the seal 10k miles later.

I recommend you get new seals.

[stryder]

There is zero motor oil visible, or "feelable" i.e. put my fingers up behind the clutch and nothing, all dry back/under there, virtually no soot.

 I turned the Getrag on end, i.e. push rod side down, on a couple of wood blocks let it sit like that for 10 minutes then slipped the drive shaft back on and spun away, back and forth even, as quickly as I could a good number of times, and notta. No seeping anywhere.  I checked the gear oil, and the level was high so I removed some. I refit the gear box just now, torqued down the mounting screw, and will let it sit like that overnight to see if it seeps.

In any case, if I get weeping overnight, I'll look to replace the gear box seals. If no weeping maybe I'll temp rig up the battery and ignition computer and run it on the stand to see if adding pressure will cause it to leak. 

Can anybody tell me what's involved...which gear box seals go on 1987 K75's?

Thanks for the comments.   

[Scott_]

You can also get gear oil up in there from it migrating up the pushrod from the back of the transmission.
I think that the pushrod seal is more prone to leak than the input shaft seal.

[Howard64180]

My low mileage K100 is also apparently leaking from the gearbox cover.  Like yours, there is no trail of oil from the input seal but thick oil has been leaking out of the weep hole.  This bike has not even been ridden for four years!   Oil is appearing at the bottom of the gearbox cover on the left hand side, with not the slightest trace of oil higher up on the cover.  Even allowing for the bike being stood, I'd expect to find something there.

I found that if I loosened the gearbox cover bolts first, they would tighten further than before, but that's only doing half a job.  I'm going to re-seal the cover. 

Obviously yours may not be the same, but we seem to have a similar experience.

[stryder]

So, I went up to my "local" BMW dealership, i.e. approx 100 miles return trip, and ordered, a rear main seal, a new clutch O ring seal, a gear box input shaft seal, and clutch push rod rear seal. The order will be approx 100.00 for the parts taxes in. They all should be in tomorrow morning. I have been, am now, and doubtless will in the future be, simply amazed at BMW's excellent parts department. Here is a 28 year old bike for which small replacement parts are still available, that do not command ridiculously high prices, and are delivered within a day. Trying doing that with any other brand. Unbelievable.

I may do the work now or wait until later as I still cannot get the gear box to issue one drip of oil. I'm not in denial that gear box oil is getting through but I  did find the oil level fairly high, too high, (I can't believe I had it so high) and may try riding it again with the correct oil level and see if that makes any difference, and if I get leaking again, will tear it down again. Not that I like doing that, but I'd like to stretch the service life of those parts for as long as I can.  :Norton:

Saw a new r1200rs while there. Gotta say, it looked pretty good. 

[stryder]

So I'm back into the gear box and have the cover off as I'll be replacing the two seals. Already did the rear seal, mucked up the outer shell a tiny bit, but inside's fine no deformation of spring or seal. A 10 MM blind hole bearing puller eventually got the old one off/out. I mucked up the output shaft seal, so I'll have to order another one. Bummer. But, what's on my mind are the end float shims that sit on top of the gear shafts. In the Clymer, it shows 4 shims, two on each shaft but I'm positive there are only three on mine, i.e. 2 on one shaft and 1 on the other in mine. The Haynes only states to pay attention to which shims are on which gears and doesn't state or show any number. I thought 1 might have stuck to the cover and spent a lot of time looking around but saw nothing. I also looked into the gearbox and saw nothing.

Is 4 shims, 2 on each shaft the norm, how the Clymer shows, or are they individualised at the factory as the Haynes infers?   

[Scott_]

I would say that it varies with the parts at time of manufacture. Only using what is needed to meet required spacing and lash clearances.

[bocutter Ed]

Mine has 3 shims.

[stryder]

I would say that it varies with the parts at time of manufacture. Only using what is needed to meet required spacing and lash clearances.

Thanks. Sounds logical.

[stryder]

Mine has 3 shims.

Great to hear that!

[stryder]

So I decide to try to get a replacement gear box input shaft seal from a local bearing house and was able to get one for less than half price of what BMW charges, so I bought 2 for good measure. The brand on the box is DMR, the number on the box is 2357-DL, the description/number on the invoice is 22X35X7DL DAE metric oil seal.

Now, to get on into the cover without damaging it. :-) 

[stryder]

So I get the input shaft seal in place with no issues, easy as pie, I don't know how I mucked it up in the first place. I guess it's held in there by the tapered bearing behind it and the clutch plate in front of it as it didn't take much force, only hand pressure, to slip it in, once slightly lubricated. And then the fun began, refitting the gear box cover. Turned out to be quite an adventure.

I smeared some silicone sealer on both sides, i.e. the box and the cover, and that was the first mistake. Should only have smeared the box's edges because I had to handle the cover much more than I expected. I'm about to start tapping it down with a rubber mallet, but am not convinced it's lined up properly so I pull if off, and with it came a shift fork pivot shaft, the one with two forks on it, I think for gears 1-4.  Lovely. So, it just slips right back in, yes? No. I can't line the forks up with the receptacle hole in the back of the case as the forks and the bottom spacer have also shifted. So I monkey around with it trying to lift and slide and slip everything back together, and a small bushing/collar slips off the lower shift forks foot/peg, that slides into the shift drum groove. Lovely.

So after thinking about taking it the the dealer and surrendering to experienced mechanics to fit it back together, I decide to use an extendable small magnet to hold the collar, and moved and lifted etc the shafts and bottom shift fork and magically it slipped back on, and lined up. All shift forks back in their grooves and both fork pivot pins nicely tapped back in, all lined up.

Before starting to refit the cover, I greased up the ends on the pins and the inside receptacles of the cover in case I wanted to lift it off to realign the cover again before tapping it down, but once the pins were refitted and aligned and the shafts aligned properly the cover went on fairly smoothly. Next time I'll know, if I see any of the shifter forks pins out of their shift drum grooves, that the shafts needed to be realigned ever so slightly before trying to refit the cover. Should see very little of those bright bushings/collars.

Man I hope this thing doesn't start leaking again anytime soon, like as soon as I fill he box up again.   :Norton:

Why do we go through these tortuous repairs on these 25+ year old K75's again? Oh yeah, their one of BMW's best ever.  :riding:

 

[Motorhobo]

I haVe pm nothing but admiration for your fortitude...btw, were any choice curse words uttered during this escapade that you'd like to share? I know which ones I would have used...like, maybe all of them.

[stryder]

I haVe pm nothing but admiration for your fortitude...btw, were any choice curse words uttered during this escapade that you'd like to share? I know which ones I would have used...like, maybe all of them.

Yes, expletives were a flying, teeth were a gnashing, but ultimately I decided to stick with it and problem solve and that extended magnet wand and a pick tool and manipulating the shafts, drum etc worked great. I imagine to myself what a dealer or shop would charge just for labour to replace both gear box seals and the rear main and am bolstered to continue to work thinking I'm saving at least a grand and probably more. I still have to get to the rear main seal as I wanted to know if the gear box was okay so I buttoned it up again, and am happy to say it shifts excellently, no harm done. I'm back down to the clutch housing now, and looking into ways to lock it up to get that big nut off, then will need to do more research on removing and refitting the main seal without special tools from BMW. More "fun".  :Norton:

[Howard64180]

If anyone else is thinking of doing this job,it looks like it's a common thing for that pivot shaft to come out with the casing, as it happened to me as well.  But I was much luckier than you, it only got half way out before I noticed; everything stayed lined up, and the collars stayed in place.  Phew.

[Scott_]

I'm back down to the clutch housing now, and looking into ways to lock it up to get that big nut off, then will need to do more research on removing and refitting the main seal without special tools from BMW.

Some have simply used a small block of wood to wedge between the clutch basket and bell housing to get the nut loose.
Or you cut yourself a piece of steel stock and make the bracket that BMW recommends.

How the new seal goes in, just remember that it does not go flush with the housing surface. Leave it proud 0.5mm (+/- 0.1mm).
There is an official TSB on this issue from BMW. #2798 and is in the forum library. It includes dimensions of the instal tool if you want to make one out of a block of wood or something.

[stryder]

I'm back down to the clutch housing now, and looking into ways to lock it up to get that big nut off, then will need to do more research on removing and refitting the main seal without special tools from BMW.

Some have simply used a small block of wood to wedge between the clutch basket and bell housing to get the nut loose.
Or you cut yourself a piece of steel stock and make the bracket that BMW recommends.

How the new seal goes in, just remember that it does not go flush with the housing surface. Leave it proud 0.5mm (+/- 0.1mm).
There is an official TSB on this issue from BMW. #2798 and is in the forum library. It includes dimensions of the instal tool if you want to make one out of a block of wood or something.

Thanks for that. Block of wood was the way I was going to try to jam the housing, so good to know I'm on the right path. Gonna have to drain the oil first.

*0.5* mms proud...Hmmm, that will be tricky.

Thanks for that information.  :Norton:

[stryder]

If anyone else is thinking of doing this job,it looks like it's a common thing for that pivot shaft to come out with the casing, as it happened to me as well.  But I was much luckier than you, it only got half way out before I noticed; everything stayed lined up, and the collars stayed in place.  Phew.

The cover came off fine when I first pulled it, didn't take any pins or shims with it. I did grease up the tops of the shaft bearings and shims before trying to fit the cover back on, and should have greased up the pins beforehand too. It's a very snug fit, i.e. the shaft bearings and the shift fork pins going back into the mating receptacles in the cover. When I pulled the cover the second time to check the alignments, the lower shift fork pin came right out with it slick as snot stuck in the cover, then the lower gear shaft shifted to the outside pulling the fork pins out of the shift drum grooves and shifting the lower fork pin spacer out of line as well. Then that little collar/bushing fell off the fork pin. I thought I'd have to pull the shift drum, but I was able to get all back together and it's working very well, no damage done. Whew...   :Norton:

[stryder]

So, I think things are okay. I've put maybe 900 miles on the bike since I replaced the clutch push rod seal, the gear box input shaft seal, the rear engine main seal and the clutch O-ring. I don't think I got the main seal to 0.5mm proud though. So far seems so good anyway, but I did get some very minor seepage for maybe two hundred miles before things got nice and dry down there, and I figure it was residual oil I didn't clean up finding its way down/through/on the joint.

What did I learn?

1) The main seal could be weeping and there not be any oil entering/puddling at the bottom of the bell/intermediate housing. My seal was leaking but the oil was dripping behind the clutch housing into spaces between the bell housing and the engine casing, which eventually seeped out of the joint between the two, and some would get blown off and "caught" at the joint between the gear box and the engine bell housing, looking like seeping from the inside. What's that old saying? "A little oil goes a long way." 

2) B.O.W. technology, (blocks of wood in various shapes and sizes) may have no limits to its applications. Used in at least five different ways during this job: to help block up/secure the bike once centre stand removed; to jam the clutch housing to R&R the clutch nut; to help drive the main seal in; to help with swing arm and bevel box installs.

3) It's very unnerving test riding your bike after replacing oil seals that if they do leak, could leak oil that may end up under your rear tire.

4) I use too much Molylube 60 for my clutch spline lubes. From now on, just a nicely worked in smear on mating surfaces once the old stuff is cleaned up.

5) Use a scribe or grease pencil to mark your clutch components positions for refitting to the same positions, not dabs of paint, which could flake/wipe off.   

6) I was reminded that synthetic gear oil really does improves shift quality. (Though I generally use syn,  last time I couldn't find any so I went with dino)

7) Though it was a huge PITA, and took up more hours than I had hoped, I nonetheless feel good about doing this at home and saving at least a grand in labour charges. The whole job cost me about 130.00, including tools and oil...plus my time and effort of course.

8) When removing the gear box cover, lift it off slowly, maybe even tap on it gently  to make sure you're not pulling a shift fork pin with it.   

Hope I'm good for another 80K.  :riding: