Leaky final drive

[billday]

Late last fall I noticed some weeping around my FD drain, thought (hoped) it was an incorrectly torqued drain.

All winter my FD's been dry while I did my spline job etc.

I refilled the FD on Sunday. Today (I haven't had the bike out of the garage yet) I found a spot of oil on the floor. The area of the drain plug is dry (should be -- it's torqued to spec with a new crush washer) -- but when I felt along the inner edge of the FD case, between the case and the brake disc, bad news: I'd struck oil.

Does anyone know about the seal that's involved? How much trouble am I in?

Thanks in advance,

Bill

[Rick G]

Not much trouble Bill you can do it yourself. Just remove the drive and disc then 8 bolts bring the case apart and the seal is easily replaced right in front of you.  Make sure to get it square and evenly inserted, level with the surface.

[motodude]

Sorry, I could not tell if it was mono or para-lever.

Rick is essentially correct.  You'll need to heat the case to get the ring-gear out.  Take your time and get the seal in evenly.  If I can do it, it must not be that difficult.

There are some good instructions on ibmwr.org: http://www.ibmwr.org/ktech/final-drive-seal.shtml

If it is a para-level, nevermind.  :dunno

[billday]

Thanks guys for the encouragement.

It's a monolever -- 1985.

Will let you know how it goes.

Bill

[motodude]

If it is a para-level, nevermind.  :dunno

para-lever, that is.

Someday I'll learn to read, type, walk, stop drooling...

[billday]

Thanks for the moral support, I did the deed today and all seemed to go well. (Let's see if there's oil under my FD in the morning....)

A few notes on the procedure here: http://www.motobrick.com/index.php/topic,580.msg9690.html#msg9690

[Uffda]

95 K75RT - 1st bike for me, everything is a first time for me on it so I am trying not to be overly ambitious regarding my maintenance capabilities.
Your posting sounds similar to my issue and your write up gives me a little more confidence to tear into it but the Clymer's manual makes it sound too challenging - special tools, etc, etc.
I'm still surprised at how the FD seems to have spewed the oil while sitting in the garage.  After a 85 mile ride home in our heat wave yesterday (90F), I put it away on the center stand, without any noticeable issues.  This morning I found a pool of gear oil under the tire, and centerstand.  The Filler and drain plugs seemed tight and dry.  I felt oil from up the rotor side.    Your thread is just what I was searching.   Was it really that straight forward?  Anything else that would commonly get replaced while in there besides the Oil Seal and O-Ring?  I may stop in at MaxBMW (CT) tomorrow for the Oil Seal and O-ring.

[billday]

Yes, the only parts you need are the seal and the O-ring (called a "gasket" in the how-to I linked to above). Max should have them. Plus fresh gear oil and a new crush washer for the drain (drain the FD before you take it off the bike). Consider replacing your rear brake pads, though -- they soaked up some oil while your final drive was leaking onto your disk.

The only "special" tool I used was a heat gun (bought years ago for stripping paint) to heat up the case to remove the ring gear/drive. Oven mitts are useful for that part. Various bits of 2x4 to support various pieces as I worked; and the all-important half-used roll of duct tape or blue painting tape.

It's not that hard, and it feels great when you're done and your K is oil-tight once again. Have fun!

[Uffda]

thanks for the encouragement.   :2thumbup: Stopped at Max today and picked up the two parts you mentioned.  Appreciate your photos of the 2x4 jig.  Have the paint stripper gun but need some good mitts.  Good call on the brake pads.  Too bad I had just replaced the pads about 500 miles ago.  I guess it is time for me to "become one with the bike" again.  After I did my first clutch spline lube in 2010, I felt pretty good about getting the bike back together with only one issue (did not know where a spring went - it was the rear brake return spring).  I hope my K bike knowledge improves further with a FD disassembly and repair.  The final test will be on my trip down to Virginia next month.

[Uffda]

I wanted to get the FD off tonight.  Prior to removing the wheel, I checked for side play and was able to move it back and forth over 1/8" at the rim.  Apparently more internal damage than just a leaky oil seal.  When I removed the drain plug to let out the remaining oil, the magnet had some metal slush AND a thin, twisted metal piece, about the length of a dime (picture attached).  Gave me a sinking feeling.  I have not gotten into it yet because one of the bolts holding the disc to the FD got stripped before it made it out.  The other one came out easily so I am guessing the PO may have had the disc off before and cross threaded the bolt during reassembly.  I have to take it in to get the bolt extracted.  Once the disc is off, I can finally see how bad the inside looks, although I still don't know what normal looks like since this will be my first viewing of it.
Anyway, my basic question for the forum experts that have BTDT, does this sound like a Bruno FD rebuild project or is it still something I can attack?   If I get it opened this weekend, I will post pictures.

[frankenduck]

Those rear rotor mounting bolts usually have a ton a Loctite on them so one coming out and the other stripping probably isn't indicative of anything.

I've never taken a FD apart but I imagine that it will be pretty obvious what's damaged once you have it apart.

[DRxBMW]

Those rear rotor mounting bolts usually have a ton a Loctite on them so one coming out and the other stripping probably isn't indicative of anything.

I've never taken a FD apart but I imagine that it will be pretty obvious what's damaged once you have it apart.

Secret of those pesky rear brake disc bolts, is to heat them with a torch before attempting removal.

BTDT without heat before, royal pain in the ass, corrosion adds another whammy.

FD's are NOT as complex as a tranny.

Did the PO ever open up the FD ?   I'm suspicious, is there a good reason why he took off the disc ?

[Rick G]

That thin piece of metal is most likely part of the bearing cage.
I would suggest a used final drive may be the way to go.
When the bearing is replaced you would need to rebuild the whole drive which is not a cheap thing to do.

[Uffda]

Those rear rotor mounting bolts usually have a ton a Loctite on them so one coming out and the other stripping probably isn't indicative of anything.

I've never taken a FD apart but I imagine that it will be pretty obvious what's damaged once you have it apart.

Secret of those pesky rear brake disc bolts, is to heat them with a torch before attempting removal.

BTDT without heat before, royal pain in the ass, corrosion adds another whammy.

FD's are NOT as complex as a tranny.

Did the PO ever open up the FD ?   I'm suspicious, is there a good reason why he took off the disc ?

It's just a guess on my part about PO since one bolt came off easily and the 2nd one stopped after a turn or 2 and did not go further, as well as stripping too easily.  I picked up the bike in 2009 with 33K on it.  PO did not think a clutch or FD spline lube had ever been done, so I went the DIY route in 2010 and did the clutch/FD spline lube at 40K.  I did another one at 60K last year and the bike has 73K on the odometer now.

[Uffda]

That thin piece of metal is most likely part of the bearing cage.
I would suggest a used final drive may be the way to go.
When the bearing is replaced you would need to rebuild the whole drive which is not a cheap thing to do.

I don't see one on BeemerBoneYard.  Bruno's site shows a K75 Bevel Drive 32/10 but I don't know if that is what my 95 K75RT uses.  Any thoughts on that, or where else to find a good usable replacement?

[frankenduck]

Most K75s have a 32:10.  Look on the top of yours near where it connects to the swing arm. It is stamped into the metal.

[DRxBMW]

It's just a guess on my part about PO since one bolt came off easily and the 2nd one stopped after a turn or 2 and did not go further, as well as stripping too easily.  I picked up the bike in 2009 with 33K on it.  PO did not think a clutch or FD spline lube had ever been done, so I went the DIY route in 2010 and did the clutch/FD spline lube at 40K.  I did another one at 60K last year and the bike has 73K on the odometer now.

Sincerely doubt your disc was ever off before.

Combo of blue loctite and corrosion makes the bolts EASY to strip, especially if there only room temperature.

Try heating the rogue bolt with a torch then a torx bit instead of the Allen. Use a long breaker bar,report back.

[Uffda]

It's just a guess on my part about PO since one bolt came off easily and the 2nd one stopped after a turn or 2 and did not go further, as well as stripping too easily.  I picked up the bike in 2009 with 33K on it.  PO did not think a clutch or FD spline lube had ever been done, so I went the DIY route in 2010 and did the clutch/FD spline lube at 40K.  I did another one at 60K last year and the bike has 73K on the odometer now.

Sincerely doubt your disc was ever off before.

Combo of blue loctite and corrosion makes the bolts EASY to strip, especially if there only room temperature.

Try heating the rogue bolt with a torch then a torx bit instead of the Allen. Use a long breaker bar,report back.

Thanks to both of you for the quick replies. I will look for the stamp.  Don't have a torx bit at home.  Bringing the FD into work and will use the tools in our machine shop.  If I finally get it split open, I will take a photo or two of the inside mess and post back here.
As a side note, I have marveled at the bike going 73000 trouble free miles and it uses absolutely NO oil between changes (every 5000).  Wish the FD could have held up as well as the engine appears to be doing.

[Uffda]

To close my hijack of Bill's FD post:
 I got the bolt and disc off.  Opened up the FD and to my eye, the ring and pinion gears seemed fine.  The ball bearing had to be shot, given the play inside there and a few small pieces found. I did not try to disassemble and get an actual look at it.  Don't know how to judge the taper bearing but that should get replaced anyway.  I have tried to resist getting in over my head on the maintenance.  Plus, the suggestion from Rick G about the bearing failure requiring a complete rebuild, made me less sure about attempting it.   I contacted Bruno about my predicament.  Sent him photos of my FD spline, as well as both ends of the driveshaft.  He assessed the splines to be okay and not in need of replacement.  It appears that bearing and seal replacements are the main issue for returning to normalcy
Bottom line - I'm boxing it up for the trip north to Bruno and let him do it right (based upon other's feedback).