Hi all,

I've just had a quick check over the bike and, as I have been expecting, the rear wheel can now be rattled slightly with hands across the diameter of the tyre, just like a dead wheel bearing. I understand this means a final drive rebuild? There is no noise or anything, just this slight movement that I believe is right on cue at 77K miles. The splines are serviceable (though far from perfect) and I'd like to keep the RS unit for originality, so..

I understand this is not a job for the home mechanic, a bit of reading shows that Jim Hill and Mike Overy (Overland and Classic) both offer rebuild services - has anyone used them for this? Anyone able to give me an idea of what kind of cost I'm looking at? Should I forget it all and just buy an unknown unit off ebay, hoping to strike lucky? Or go stark raving mad and fit Paralever gubbins?

Thanks

EDIT: Actually it does sound kinda rough, maybe because I'm now checking it cold. Oh dear oh dear..

Gwan, Jack - fix it yersel'.

My bearing was replaced without removing the final drive unit........

Don't leave it because your bevel gear etc should be ok but still needs someone who knows it to confirm that.

Dai wrote:Gwan, Jack - fix it yersel'.

Believe me I'd love to, but the Clymers manual tells prophesies of endless torment and soft hammers and heat guns and about 12 special BMW tools.. Though it also says these units are bullet proof and good for 150K+ miles. Maybe on some 60HP boxer!

Olaf - I intend to not use it at all until it is fixed, using it is just asking for big trouble. My manual shows the steps for a full recondition but I don't want to do all that, it does look as though the bearing could be removed without too much hassle but the manual does not describe this particular process. I do find myself wondering if there is a serious shortcut to all this, though the seal behind the splines does leak slightly too.

Of course there's always something like this, pretty sure I could get the maintenance lads at work to get the rest of that bolt out. The splines look very similar to what I already have though, perhaps total failure is imminent..

Snod Blatter wrote:

Dai wrote:Gwan, Jack - fix it yersel'.

Believe me I'd love to, but the Clymers manual tells prophesies of endless torment and soft hammers and heat guns and about 12 special BMW tools.. Though it also says these units are bullet proof and good for 150K+ miles. Maybe on some 60HP boxer!

Olaf - I intend to not use it at all until it is fixed, using it is just asking for big trouble. My manual shows the steps for a full recondition but I don't want to do all that, it does look as though the bearing could be removed without too much hassle but the manual does not describe this particular process. I do find myself wondering if there is a serious shortcut to all this, though the seal behind the splines does leak slightly too.

Of course there's always something like this, pretty sure I could get the maintenance lads at work to get the rest of that bolt out. The splines look very similar to what I already have though, perhaps total failure is imminent..

That eBay one looks fairly rough, but the price probably reflects that.  As you say though, would you be buying another failure in waiting? The speed sensor bolt should be easy enough to drill out as, with the FD off bike, there are none of the usual access issues with getting a drill in at the right angle. Depends how good you are with a drill (or the skills of the lads at work) - use plenty of cutting fluid and don't go too deep. I assume that it is a blind hole (i.e. hole doesn't go all the way through to the inside of the FD) in which case beware of over-zealous drilling! Helicoils may be your friend if you have to drill oversize - but nothing to be feared there, I successfully used helicoils for the first time a few weeks back and found the experience far more satisfying than drilling and tapping to use a larger bolt!

See Neal Cooper's very recent post on a similar issue and link to MikeP's how to do it (with colour pics) - looks like changing the main bearing on your current FD should be no great drama...but don't come hunting for me with a heavy wrench when it all turns out impossible, this is NOT a job I have personally done yet!!

The Clymer is for a full rebuild. To do the bearing only to put it bluntly is a cinch. Trick is disturb nothing, do it from wheel side and check the resistance as you finish. I watched it being done. Unit was never taken off the swing arm.

92KK 84WW Olaf wrote:The Clymer is for a full rebuild. To do the bearing only to put it bluntly is a cinch. Trick is disturb nothing, do it from wheel side and check the resistance as you finish. I watched it being done. Unit was never taken off the swing arm.

Everything's a cinch when someone else is doing it! I'm sure I could show Rossi where he's going wrong..

How did your guy get the bearing off? With a puller or just lever it off a la MikeP?

Certainly it costs nothing to take the unit to bits, and there is nothing to lose as it's useless right now, so I'll at least have a go at it. After this week I have two weeks booked off work with nothing particularly planned other than a valve clearance check on another bike, so this will be something to do. Lucky me, eh?

Once its fekd no option but to take it apart. We knew mine wasn't fekd.

Dai wrote:Gwan, Jack - fix it yersel'.

There was always an air of inevitability about this..

Drained the oil, there was a fair amount of silver/grey but the bolt was not furry and nothing extra seemed to fall out of the hole. Good start.

Getting these out was the worst part of taking it to bits. They weren't even threadlocked in, just someone had put them in with loads of dirt left in the threads. I can't really believe that all the rear braking force goes through these two little screws..

The first real surprise was that these bolts were actually loose. I set myself up for more heaving and worrying about allen bolts rounding out, but they just turned right out. No real effort required. Is this normal because the bearing has collapsed slightly, or has some pillock been here before and just not done them up enough? Not a drop of oil ever leaked out but it's still concerning.

Special tools..


At the 10 o' clock position you can see some roughness on the aluminium casting, the same area in the other half is also rough. This is where the loosest bolt was, I think the whole lot has been slightly rattling around!

Bock bock in the middle with the special tool and..


The crown wheel bearing does feel a bit rough, but I've felt bearings that were much worse. Perhaps it would feel worse if I cleaned all the gear oil out of it. Thankfully it has not spun (or had the cage break up) so it is still very much a tight fit on the crown wheel, unlike the ones that someone else has on here - was it audibob who found his could slip off? Otherwise I can't see any chips in any teeth and the taper roller on the end still seems nice, so it looks like I just have to replace this crown wheel bearing and slap it back together. It looks way under spec to my eyes, narrow and yet the wheel is stuck way out where it can cause a lot of force to go through all this gubbins. Could it not have been double race? Anyway, time to bag all this up and start looking at who can provide me the bits for the least money

Herr Blatter, the braking force doesn't really go through those two little screws.  Rather it is constrained by the four wheel bolts.  The screws are only there to hold the brake rotor when the wheel is removed.

just be aware that you may need to fit a new crown wheel seal after the repair

and don't forget to lynish the running surface of the seal on the crown wheel  before you replace the seal
I see so many folks complaining that their new seal is leaking ...likely because they are trying to replace a seal now running on corroded or just plain dirty road crud affected metal ...as I have done once myself .

the design of the bevel box is an engineering delight ...who wants a standard swing arm double sided , with typically under designed plastic bushes on the main pivot point axel ...chain drive and all the rest of that stuff that sits in the crud of the affor mentioned chain drive ...these bmw things are designed to be different for a good reason
I delight in the fact that I can take my k bike to the tyre guy  sit it on the centre stand and have the wheel out in under 5 minutes by myself , just a few screws  and nuts to release the plastics . and back on in the same time ..instead of fighting to withdraw the main axel , and swingarm adjustment tensioners ,holding the chain in the right pace to fit it back together with 3 or 4 hands needed , grease , slime and dirt on disks , axels nuts and shafts ....f^^k that stuff

there are so many folks with broken mindsets about what is good and bad ...if any deviation from vertical (closed mind )  designs then it must be broken to start with ...hmm .

good luck with the repair , but remember the cheapest may not be the best option ...

I fully intend to replace the seal, and the O ring that goes between the case halves as mine is all twisted and chewed up (which also makes me think some pillock has been in there before). I should also perhaps mention that the previous owner was a Grade A pillock and slathered copper grease all over the drain bolt before putting it back in, so this FD has been gently chewing copper for the past 20K miles or more. He is a policeman though, perhaps I should've expected it..  

Lynish = polish?

linish ...sorry my bad

https://en.wikipedia.org/wiki/Linishing

in this case cutting back the surface to obtain fresh clean metal below the embedded corrosion and pitting in the existing metal ...also allows for the new seal to cut into the metal to create its own running seal line ...if you get my drift

agree policemen and teachers ...an enigma indeed

Oh okay, I don't really have any equipment to do that.. Will some Autosol do?

possibly a good wet and dry coarse grit paper would do, followed by a finer grade . but those crown wheels are hardened ...takes a good deal of effort to do well

good luck

The best way to do the seal surface is firstly check out the surface for a groove. Run your fingernail across the seal surface, if you feel any groove then further attention or at least opinion will be needed. If there is no groove then use a green scotchbrite pad and some autosol or just cutting compound for paintwork and polish in the direction the seal runs i.e. round the surface not across it, Try not to use wet/dry sandpaper as it can leave grit embedded in the surface unless the correct procedure is followed to get rid of it. Usually using wet/dry paper on steel is not too bad but on brass or bronze it's a disaster.
The seal surface should be as smooth as the new bearing like butter or a nubile butt.

yep still need to brillo pad the shaft after any work to it ..must be impeccably smooth  and cleaned of any residue

Today I have procured a 17 ball NTN bearing and a seal and an O ring from Moto-Bins, and then found out neither I nor the bloke next door have a puller with small enough claws to get between the old bearing and the crown wheel. So I thought I'd put some wheel nuts in, stick it in the vice and lever it off MikeP style. Yeah right!

I thought I'd try some heat and some long bars but it won't even pretend to budge.

I am actually concerned about cracking the crown wheel, which is probably stupid but that is how destructive it feels.

I am considering phoning the now-retired "Boxer Man", see if I can buy a puller off him that will do the job. Anyone tried contacting him in his retirement? Or got a particular tool that fits and isn't too expensive? I already have the rattle gun, just need a puller..

Snod Blatter wrote:, and then found out neither I nor the bloke next door have a puller with small enough claws to get between the old bearing and the crown wheel.

When it's a tight space like this, search for a bearing separator/puller.

Cor they sure are expensive if you want to pull a 12cm diameter bearing.. Cheaper ideas are welcome

my final drive had a very small amount play but a horrible whine which would drive me mad.

The stub shaft on the crown gear set which the small taper bearing sits on was shiny, I could pull it off fairly easily.

Cant remember having any play on the big bearing 

Spoke to Jim hill, but he was very  busy so time was an issue as I only have one bike, so I changed to a 16 spline shaft and a very low mileage drive from James Sherlock three days later

I looked into trying to remove the crown bearing , but that would have meant hiring a puller, plus the wear on the stub shaft meant another rear drive for me.

I  have just replaced my rear main seal and o ring so am reasonably ok with spanner work, but for some reason I just didnt fancy doing it, even if my unit had been  serviceable 

Good luck with your rebuild snod

So! I went to some lovely guys at Sinroja in Leicester and they pressed the crown wheel bearing off, and then froze the crown wheel and heated my new bearing and on it plonked. I would never have got that bearing off, he was giving it some welly with the press and he had to spend a few minutes on it with a blow torch.

I got home full of enthusiasm and whacked it all together, the halves of the casing didn't want to go together but with a bit of grease it was okay. I put the disc on, all seems good, put the wheel on, torque up the nuts.. And I can still feel a sodding wobble. It's not as much as before but it's not far off. I am annoyed.

I can pull the wheel straight towards me from the side and it doesn't move a bit, so it's not like it's massively under-shimmed (maybe?), but one hand at 8 o'clock and one at 2 o'clock and it still clonks around. Right after use I cannot feel anything, but over time (as if when the oil drains out of the way) it comes back. Is this the taper bearing? Is my casing perhaps not as tight on the crown wheel bearing as it should be because the bolts were loose? Certainly the bearing doesn't slot in but maybe it should be even tighter. I don't know. Did I mention I am annoyed? I'm £65 down with nothing to show for it..

When you put it back together the big bearing needs shimming. Before you put the wheel on you can run a test on it. When you tighten it up there must be a little resistance to the hub turning so that you have no play. He went at this a few times to get it right. Seems you may still have some play or bearing isn't in exactly square. My friend ran all the checks before putting he wheel on. Its done 10k miles since and I know its good because on a long motor way run its not generating heat and running much cooler than before. I have a habit of feeling the temperature of hubs and bearings after a run, a habit developed from towing boat trailers. Heat means trouble.

There was noticeable resistance to the hub turning, I tried it before putting the disc back on. But that might be thanks to the new output seal, it's hard to know how much resistance is normal, how much there should be etc.

Being a bit rough with it I may be able to feel a slight clunking straight sideways, pulling away from the FD, so perhaps it is shims. It was part of the plan to measure the gap but then I read on here that you don't normally need to change them.. Bugger. Anyone got any tips on measuring for required shims? I've seen it done with a dial gauge but the bloke at the cafe racer shop said they use feeler gauges, not quite sure how though.

I've about had enough now, give me a couple of 6302s to hammer into a wheel any day over this. What a nightmare for a home mechanic.

Me again..

Since the unit is together I figure the only reasonable course of action is to measure the play "Dman" style, levering the crownwheel out of the FD and using a dial gauge to measure how far it comes out. The only realistic way to do this is to take the FD off, so after forgetting that I shouldn't let the swingarm fall down on to its stop (FFS) I find my FD splines look like this:

This is basically toast, right? There is also a fair bit of gear oil inside the shaft housing, enough to be dripping out consistently while I undid the 4 bolts holding the FD on. Cor I wish I'd bought a whole Paralever setup and banged it on right now.

For what it's worth, initial "Dman" testing reveals I can't feel any movement in there so I may just need a shim to add preload, which would be consistent with the small amount of wobble I can feel. We shall see what the dial gauge says, though I definitely can't feel it popping out or back in like the video from the LT forum that shows this..

It is also concerning me that everyone else doing this finds they need less shim, while I seem to need more. But then it all seems to be about boxers..

Not your day, is it? At least you found that before the buggers stripped and left you stranded in the middle of nowhere.

I should've checked it all out before proceeding, really. There are a few bits of the final drive which don't last, and if it needs a rebuild for whatever reason then I would recommend to anyone else to take a good hard look at what they have and decide if it can be patched up or if wholesale replacement might be the better way to go. A reliable bike with life left in it is better than an original bike that might fail.

Anyway, I have been hard at work yet again - so much for this week being a holiday! I opened up the FD yet again, heated the case, let the crown wheel and bearing fall out, cleaned it all of oil and grease and then put it back together still with the shims in place. I then set about checking the play "Dman" style:

Top tip for anyone else trying to do this - use the shock absorber bolt to steady the FD, otherwise it rocks all over the place and you'll never get a repeatable reading. I also used a magnetic base for my dial gauge stand which sticks most excellently to old car discs!

Levering the crownwheel upwards and then knocking it back with a small hammer (sorry bearing but what else can I do) I quite reliably get 0.12-0.13mm of movement. It is my understanding that we want 0.05-0.1mm of preload so I want a 0.2mm shim. Remember this is on top of the shims that were already in there, which seems the total opposite of what everyone else finds but hey, they don't ever seem to be doing to to 8v K100s.

So, frankly, I'm going to order a 0.2mm shim from James Sherlock, put it all together and wait for a nice low mileage RS monolever/paralever set to turn up on ebay. Bugger it all.

Don't go thinking a Paralever will solve the problems. All these bikes are around 30 - 35 years old and will have problems. Take the drive to an expert, they are not an easy thing to setup and need to be correct before they will work. Just putting a new bearing on can change the meshing of the gears.

if you have had some movement before , why assume that the shims are still in good order and haven't suffered from some wear or compression

I think you are on the right path to obtaining the correct preload with the new additional shim

I would have suggested changing the beveled bearing as well whilst in there , I got one locally for not too much money , but removing the shell could take a little persuasion and tricky tactics .  then do the measurements for the preload - shims

once that has been achieved possibly the mesh to the gears from the pinion may need recalibration ....

just thinking aloud

good luck

RicK G wrote:Take the drive to an expert

¿No comprende señor?

I understand that Paralever is essentially the same design and, if anything, has extra failure points added but there do seem to be more low mileage Paralever parts around than low mileage Monolever parts, for whatever reason. Plus all the extra gubbins looks pretty cool, right?

Also the guy at the cafe racer shop in Leicester was surprised that I wasn't going to replace the taper bearing, they do this as a matter of course. But, eh, whatever..

Anyway! Annoyingly James Sherlock are quick on the posting-things side, so yesterday my new shim arrived. I was secretly hoping for a day off to let my knuckles heal a bit but it was not to be. So, put the shaft back in. Once it's covered in moly I can't see the splines any more, so that's one problem dealt with!

Fit the FD back on the swingarm so that I can undo the bolts without it scooting around all over the floor..

While it was in bits I thought I'd pay some attention to the old shims, like finding out how thick they are. This led to an interesting discovery - one is bent! I'm pretty sure it wouldn't come from the factory like this, so despite not having a receipt for any FD work I really suspect this has been done before.

The new shim is top right, bent in a similar manner due to its journey through the post. Interesting how it's not as wide as the others, for some reason I assumed that £11 would get me an original BMW shim. How silly of me.

If anyone is interested, the old shims were 0.5mm and 0.2mm so I have added quite a significant amount with an extra 0.2mm. I don't know how much shim these normally come with from the factory.

Heat gun use intensifies..

With the unit back together (moments before it began to rain, phew!) I put a bolt in the hub and gave it a bit of a turn. Sure enough, as Olaf says, it was significantly stiffer to turn than before. Almost to the point where one finger would not be able to turn it. Whether this is too tight or not, I don't know. I just know it's different.

I put the disc back on, and it felt solid. More solid than before. I put the wheel on and it was still solid, zero play. I filled it with oil and churned it round for several turns.. Still solid! So I went for a test..

20 miles later it's still solid, no wobble at all. Hopefully this is all over now! As a bonus, pushing the crown wheel slightly further into the pinion has slightly reduced the lash in the drive train, which has always been a bugbear with this bike but again I don't know if having more lash than a really loose chain is normal for these. I also cannot detect any whining (only a bit from the gearbox) and, while the unit does certainly get warm, I wouldn't consider it hot and I'm pretty sure it's no hotter than it was before though I never checked it very often. Overall, so far, I'm a happy bunny.

So, what did we learn?
1) This isn't really a job for a home mechanic. It is certainly not "a cinch". If you happen to have a garage bristling with tools, including blocks of wood and relatively clean rags and a dial gauge with a steady stand then you might be able to muddle through but it is still quite difficult and you will likely need help getting the bearing off the hub anyway.
2) Check out the whole unit before deciding if it's worth patching it up with a new bearing. There's a good chance the splines will be heavily worn by then too and there are still a load of FD units out there at reasonable prices (for now!).
3) Expect to have to re-shim it afterwards.

It has been quite a journey, I hope this thread will help others if they fancy a go themselves

Well done Jack! I've never done a K drive but had lots of (not) fun rebuilding Moto Guzzi ones.

Have you checked the meshing pattern of the gears, if it's not right you could well be in for more fun down the track.

Cheers Dai, are Guzzi units similar?

Rick - I have checked nothing, I was quite happy that it went round when put back together and happier still that it wasn't noisy. Dare I ask, how would I check it..?

I think it is now probably closer to how BMW meant it to be than before, the gear teeth on the crown wheel are not perfect and show signs of rubbing and swapping metal with the pinion gear plus it had (even) more lash previously. If this will last 20K before failure then I'm fine with it because realistically the splines aren't going to last that long.

You use engineers blue to check the mating surfaces but if it isn't making any noises and little backlash then it probably will go the distance.

Ah man no, I'm not doing that. Can I use this moment to employ the Aussie "she'll be right" rule?  

Right, time to change the oil again to try and get rid of any rubbish that will inevitably have found its way inside (and get rid of some more of the copper grease!), fill 'er up with lovely synthetic and carry on. Shame it's raining again..

Guzzi units are relatively easy to get apart, but there's the same hours of buggering about to get the backlash and mesh correct. The real sod is when the inner oil seal gives up; fortunately that's very, very rare and there are shedloads of forty+ years old Guzzis still running around with the factory fitted seal. If one does go, you're into a whole world of grief with inner bearing pullers, drift tools and - most important of all - the oven in the kitchen.