getting the gearbox out for repairs on my '96 1100RT

[schneeman]

oh man, i am going nuts with this thing, i just went to recheck everything, and discovered that the input shaft DOES have a little axial play, a fraction of a millimeter, but it's there, and i can distinctly feel what i assume is the end of the shaft touching the bottom of the case. It is springy, goes right back. The lid is still off.

When assembled correctly, does the end of the shaft touch the bottom of the case ? Probably not. If not, then the bearing might be a bit worn and needs replacing ?

 

Guess i will have to dismantle everything again tomorrow and recheck everything and investigate the state of the shaft bearing and how it fits in the case. Oh well...

[schneeman]

Today i took the input shaft apart, turns out both bearing have a play, i can move the inner race with respect to the outer one.

I am guessing that can happen when the bearings operate under an unnecessary preload that causes stress inside on the races ?

Anyway, made a mistake of buying two 6205-2RS instead of one 6205 and one 6304, so now i have to wait a day or two for the other one to come.

I put the 6205 on the shaft, after freezing the shaft and heating the bearing it jumped right on.

Here are the pics of the shaft parts and the bearing & gear

 

 

 

 

 

 

In the upper left part of the gear you can see that there's a flaw on the surface of the race, similar to rust surface damage, it's not deep, but it's there. I don't suppose it matters much and i don't intend to discard the gear because of it. Apart from that the gear didn't eat into the bearing like it is common on the 97 shafts, the axial play was due to the play in the bearing itself.

In the manual they say i should use new lockring on the shaft, but since there's nothing wrong with the one that was there i plan to reuse it.

 

 

 

 

 

 

[greenrider]

At least they are a very common bearing. We have those on the shelf at work.

I find it interesting that they have sealed bearings in a transmission. I wonder why?

 

I have found this very interesting and thanks for all the photos. They are worth a 1002 words.

[smiller]

I find it interesting that they have sealed bearings in a transmission. I wonder why?

The early transmission models used tapered roller bearings instead of caged ball bearings, and the former was really a better choice for this application. No one knows why they made the change but setting the end float on the sealed bearings is a much easier procedure than setting preload on the tapered bearings so it has been suggested by some that the change was a cost-savings measure (less time to assemble on the production line.) But as always with BMW all you can do is guess.

[dan cata]

I find it interesting that they have sealed bearings in a transmission. I wonder why?

 

I think some of the bearings have their own grease and do not use the gearbox oil for lubrication.

 

Dan.

[nrp]

It may also relate to the contamination buildup from gear clash etc. Having a common lube source (i. e. open bearings) means tramp metal from the gearbox gears will get fed thru the bearings, gradually wrecking them. It may have been a life issue.

 

Another tradeoff though is that grease lubed bearings are not as able to take high rpms.

[smiller]

It may also relate to the contamination buildup from gear clash etc.

It might, but... to my knowledge there wasn't any problem with bearing failures in the M93/M94. That didn't start until they switched to the 'clean' caged ball bearings.

[SKYGZR]

For any kind of "sealed" roller bearing, one can remove the rubber seal ring(s) with a small pick type (dental) instrument, or small, thin, flat blade screw driver, yet the "pick" is easier. Once they are removed, a solvent tank, or other (coffee can) type recepticle, degrease solution, and brush,can be used to "wash/clean" out the old grease.

 

One will be amazed at how little grease actually resides in these type of bearings. Once clean and dry (with canned air, or from a compressor), they can be fully repacked with your grease of choice, and the seal rings re-installed.

 

Once cleaned/washed/repacked, they will preform way better than when installed, and or purchased.

 

(From experience rebuilding numerous mounts for the telescope(s) systems I currently have in operation.)

[schneeman]

Waiting for the parts to come, i pulled the 97 input shaft apart.

There's hardly any wear on the bearing form the gear, i was expecting more. It is comparable to the state of the 94 shaft bearing. The 97 gearbox had 90tkm on it as opposed to 60tkm on the 94, then again the 97 has been opened before, so parts could have been replaced.

If this is the original shaft+bearing and that is what it looks like after 90tkm i think i could have just used this shaft. But since i took it all apart i will try to make the best gearbox i can form the parts i have.

 

BTW, the 97 and 94 (with clean bearings) boxes differ only in the shaft designs, right ? So in principle, the easiest and cheapest way to fix the gear-skipping issue is to open your 94, and put the intermediate + output shafts from a 97 box, which you can get second-hand for about 100$ each. Plus replace worn forks etc.

?

If this is true, i think i might be doing just that, since i know my 94 was aligned perfectly, with the splines in excellent condition, all the switches were working, seals were tight etc.

The spline issue is a bit of a mystery, so sticking to what i know worked is the safest option.

 

 

[smiller]

BTW, the 97 and 94 (with clean bearings) boxes differ only in the shaft designs, right ? So in principle, the easiest and cheapest way to fix the gear-skipping issue is to open your 94, and put the intermediate + output shafts from a 97 box, which you can get second-hand for about 100$ each. Plus replace worn forks etc.

?

Unfortunately, no can do. The bearing size on the intermediate shaft is different in the two versions so they are not interchangeable.

 

Re: the input shaft bearing wear in the M97, it's weird... I've seen some with severe damage in less than 40k miles and others that go well into triple digits without a problem (although most will see the issue somewhere within those bounds.)

 

[schneeman]

Unfortunately, no can do. The bearing size on the intermediate shaft is different in the two versions so they are not interchangeable.

 

Thanks smiller,

still, i just checked and the bearings are the same in the version of the 94 i have, namely 47mm and 59mm in diameter of the two bearings, exactly as on the 97 intermediate shaft i have.

Perhaps because this is the late 94 version with clean bearings ?

Or maybe i'm not getting something here...

 

[smiller]

still, i just checked and the bearings are the same in the version of the 94 i have, namely 47mm and 59mm in diameter of the two bearings, exactly as on the 97 intermediate shaft i have.

Perhaps because this is the late 94 version with clean bearings ?

Yeah, I guess. All the ones I've seen are as I described but that could have changed in the very late M94s as these were a kind of hybrid unit.

[nrp]

Re: the input shaft bearing wear in the M97, it's weird... I've seen some with severe damage in less than 40k miles and others that go well into triple digits without a problem (although most will see the issue somewhere within those bounds.)

That may also have something to do with the clearance in the engine's rear main bearing, as well as engine-transmission alignment.

[smiller]

The reason the input shaft bearings fail (particularly the rear one) is due to a poor design in the transmission itself. The helical drive gear rests directly against the rear bearing with no thrust washer, and with a narrow contact area that concentrates contact force. Add this to the slight but constant hammering caused by the torque compensator spring and eventually the inner race of the bearing is deformed. You can see that process just beginning in the pictures in this thread, and it eventually gets worse to the point of causing early bearing failure.

[nrp]

The reason the input shaft bearings fail (particularly the rear one)..........

You mean the front one?

[smiller]

I was talking about the rear one, adjacent to the drive gear.

[TeSmSp]

Are ceramic bearings suitable for this application?

[smiller]

I don't know. But the problem is not due so much to the bearings wearing out as their being physically damaged by the process described above. I think an alternate bearing type might be just as susceptible so I'm not sure what you would gain.

[schneeman]

Yesterday i reassembled both the M94 and M97 input shafts with new bearings, no axial play anymore.

Today i reassembled the M94 gearbox with the intermediate + output shafts and one shifting fork taken from the M97.

After measuring it turned out i need one more shim for the input shaft, so tomorrow i am going to go and get it, the other two shaft could be shimmed to 0.1 mm play with the combination of the shims i already had from the two gearboxes.

When put in neutral the gears do what they are supposed to, so i hope i assembled it correctly.

 

So hopefully tomorrow i will be able to finish reassembling the box, and then it's back to the garage to put it on the bike. I do have an important job interview in the coming weeks so i need to prepare and learn quite a lot of stuff, hence i cannot spend all my time on the bike (which i would prefer )

 

 

 

final hybrid gearbox:

[AnotherLee]

Ahh - it's a thing of beauty, Schneeman.

Thanks for the pictures & the thread.

How are you measuring end play?

[smiller]

Good job. I see you installed the oil baffle, you don't want to get the cover nicely installed, stand back to admire your work, and then notice that part sitting on the bench... DAMHIK...

[schneeman]

Ahh - it's a thing of beauty, Schneeman.

Thanks for the pictures & the thread.

How are you measuring end play?

 

You're welcome, thanks for your comment.

I use one/two 12x42mm parallels to build a platform from which i can use a sliding calliper to do the measurements, the key with this method for me is to take my time, and carefully repeat the measurements again and again, changing the location of the parallels and varying all i can vary to make sure i get as much statistics as possible, and then take an educated guess as to what the distance actually is. With a little investment, like a proper depth gauge, it can be made easier i guess.

Initially, on the M97 box, i used two methods, one to measure the depth of both halves of the case and the length of the shafts bearing to bearing (outer races), and the subtract the two. Then i repeated the measurements after installing the shafts, i.e. how much they protrude from the box and subtract that from the depth of the lid. They both gave same results to within my measurement error, apart form the input shaft and that was due to play in the bearings. Now, with the hybrid gearbox, i just installed the shafts, tapped them a bit with a plastic hammer to make sure they sit properly (with the input shaft i use an aluminum rod positioned against the outer race of the bottom bearing), and then measured how much they stick out, confident from the previous efforts that this should be ok if done carefully. In the end i'm not 100% sure it ok, but i'm pretty sure it's close, so even if i'm off it's not dramatic. Hopefully.

 

I see you installed the oil baffle, you don't want to get the cover nicely installed, stand back to admire your work, and then notice that part sitting on the bench... DAMHIK...

 

i do get paranoid sometimes, did especially in the beginning, where i would go to check things out every couple of hours, come up with a new idea about what i might have screwed up and then go investigate. Today i frantically went looking for a nonexisting washer, thinking there was one on the shifting roll

 

Cheers

[brasscap]

Great info here as I will be referring to it for my teardown soon. I discovered drops of fluid a couple of days ago so I went to a local indy shop and they confirmed what I thought. Kind of scary and intimidating since I have never delved in this far and can't afford to pay someone else to fix it. Winter here is great for riding and I want to get her back on the road! I will be a better shadetree mechanic or a good candidate for the looney bin.

[schneeman]

The shim came today so i was able to put the hybrid M94/M97 gearbox together.

No parts left !

 

Seems to work as it's supposed to, hope i didn't screw anything up too much.

 

Starting tomorrow i will be reassembling the bike, on the way i will bleed the ABS unit, maybe change the brake lines to stahlflex, fix a non-working rear brake light switch. Then valves + TB sync (i cleaned the TBs, and accidentally screwed the throttle cable sync), oil change, spring, and i'm ready for a test ride.

 

 

 

[philbytx]

A thing of beauty !!!!

[schneeman]

Had some time today, so managed to put the clutch and gearbox back on the bike.

 

Used moly grease to lube the parts as specified in the manual. I centered the clutch disc with the M97 input shaft i got left over, useful.

It was a bit more effort to put the box back on than it was to take it off, I used guidepins and a bit of patience.

I imagine putting the gearbox back is when the bike tips over forwards when not secured, it would have happened to me today if it wasn't for the woodblock under the engine.

 

Clutch back on:

 

 

Gearbox back on:

 

 

 

 

 

[schneeman]

Reassembly in progress...

 

[Edgar]

Hope you adjusted the clutch before you put the drive shaft on as it's so much easier when you have such great access. Cleaning and lubricating the gear shift linkage before the plate goes on or shortly there afterwords is good. While you have access to the shift lever make sure that it is centered in the shaft and that when it shifts it doesn't foul on the top or bottom.

[Selden]

It was a bit more effort to put the box back on than it was to take it off, I used guidepins and a bit of patience.

I imagine putting the gearbox back is when the bike tips over forwards when not secured, it would have happened to me today if it wasn't for the woodblock under the engine.

Too late for you, but when I replaced the clutch about a year ago, I strapped the transmission and swingarm to a home-built dolly, and wheeled it back from the engine. When it came time to put them back together, I used a ratcheting tie-down strap to bring them together, very slowly and carefully. A small bottle jack allowed me to fine-tune alignment of transmission and engine. Slow, but no drama.

[schneeman]

Yesterday i got to addressing the non-working rear brake light. I noticed it just before winter, first, the brake light was stuck on, and when i worked the rear pedal and cleaned the switch metal plate area, light went out, and never came back.

Front brake operates the brake light ok, so i thought it is the rear brake light switch that went south. But today i checked the switch and it seems to be ok, meaning it conducts current when un-pressed and doesn't when pressed.

Since the front brake works, it must be something in the wiring i guess. WIll go back to the bike with multimeter and see if there's electricity going to the switch , i hope i won't have to take it all apart too much.

[schneeman]

Still waiting for the replacement rear brake light switch, turned out the old one was faulty afterall. In the meantime, i attended to the front brake master cylinder that has been weeping for a while apparently. I didn't buy the bmw repair kit, ridiculous that they want you to buy the whole piston while all you need is the two seal rings, it's bs. Anyway, form what i read it solves the problem only for a while, and i am inclined to suspect that proper cleaning will do just the same provided that the seals are undamaged. I used some very fine sandpaper to polish the inner top part of the cylinder and got it smooth to the touch.

 

The paint is gone in some places, but it's not really visible since it's underneath the setup. WIll see how long before it starts weeping again...

 

 

very dirty

 

 

 

 

 

 

after cleaning

 

 

 

reassembled

 

 

 

 

 

 

 

[dan cata]

Had that on my GS. I cleaned the pump and put it all back together. It did last a couple of more months, but it started to leak again in the end...

 

Dan.

[schneeman]

Had that on my GS. I cleaned the pump and put it all back together. It did last a couple of more months, but it started to leak again in the end...

well then i guess i can expect the same, will see

 

 

today i installed a new rear brake light switch, bled the ABS and at calipers, put new fuel filter and reassembled the bike to the point that i am ready to start the engine and do the valves and TB synch. nice.

I was expecting gunk to come out of the ABS unit but it came out clean, this might be an area that the bike saw some maintenance before i bought it.

 

fuel filter

 

 

 

 

 

[dan cata]

If you bleed the calipers first, 99% of the fluid will be fresh in the ABS unit

 

Dan.

[schneeman]

If you bleed the calipers first, 99% of the fluid will be fresh in the ABS unit

i bled at calipers last year when i got the bike, fluid was brownish a bit initially.

this time i first bled at ABS, then at calipers

 

here's a little movie of the front brake abs controller bleed

 

 

[schneeman]

The old fuel filter, i cut it in half to check it out.

The silver particles came from sawing.

A new filter is supposed to be yellowish, i can see that at the edges. Must have been there for a while. Hope the engine will run noticeably better now, it was a bit sluggish at high revs compared to my ex 1100R.

 

 

[schneeman]

Did the valves yesterday, synchronized throttle bodies today, and the bike runs great. I think new fuel filter made a difference, engine runs nicer and accelerates happily. As with my previous boxer, i simply stop trying to make it run smoother when i reach a satisfactory level, not when it's done perfectly, since after 1-2 h on the road (twinmax) stopping and adjusting, i start chasing my own tail. There are vibrations especially above 5000 rpm, but acceptable i guess. Boxer charm.

 

Gearbox works ok so far, seem to find a false idle between 2 and 3 easier than before, more positive shifting should remedy that. Only rode to do the sync, will have better impression after some longer relaxed ride. Tomorrow

Weather is great, finished just in time !

 

 

[AnotherLee]

Great looking bike, schneeman.

Especially when compared to the earlier pictures with the tail up and wires dangling!

[brasscap]

You did an excellent job! Now it's my turn to finish mine.

[schneeman]

You did an excellent job! Now it's my turn to finish mine.

 

looks like you're halfway there

good luck !

 

nice workplace btw, makes the job much more pleasant

[BrotherMotif]

Great detail on the repairs.

Would you be able to show a simple checklist of what must be done for the transmission conversion? I've seen posts on boards with "m94 to m97: same internals, just shim stuff inside."

You've had the most detail on your specific model but I can't find a checklist that anyone can use when doing the upgrade. I'm in a pinch and need to buy a new housing or my bike is toast.

Thanks for all the hard work!

[schneeman]

Great detail on the repairs.

Would you be able to show a simple checklist of what must be done for the transmission conversion? I've seen posts on boards with "m94 to m97: same internals, just shim stuff inside."

You've had the most detail on your specific model but I can't find a checklist that anyone can use when doing the upgrade. I'm in a pinch and need to buy a new housing or my bike is toast.

Thanks for all the hard work!

 

Hi BrotherMotif,

I do not have general knowledge about different models of those gearboxes, i found that in my case all the shafts were directly exchangeable with the M97 since it was the last batch of the M94 boxes. So i ended up just putting the intermediate and output shaft from the M97 into my M94 box. I imagine that that's not always the case as the M94 input shaft won't go into M97 housing unless you change the bearings etc. As far as i know, apart from that all other components, shifting roll and forks etc are the same for both models.

Anton is the gearbox guru and he will be able to help to a much greater extent than I.

Anton

 

Cheers !

[smiller]

Would you be able to show a simple checklist of what must be done for the transmission conversion? I've seen posts on boards with "m94 to m97: same internals, just shim stuff inside."

You've had the most detail on your specific model but I can't find a checklist that anyone can use when doing the upgrade. I'm in a pinch and need to buy a new housing or my bike is toast.

The M94 and M97 are very similar but not all parts are interchangeable, and add to that the fact that there were some hybrid M94/M97 models produced during the changeover year and things can get confusing.

 

With that said, in general: You can install an M97 input shaft in an M94 (and vice versa), although (unless you have one of the hybrid M94 models with the 'clean' bearings) you will need to install a spacer in the case cover when installing an input shaft with clean bearings in an M94 case. But it's a simple operation and the spacer is still available from BMW I think. So, if you have a standard M94 and you want to install an M97 input shaft all you need is the spacer and a set of input shaft bearings (6205-2RS), or BMW will sell you a kit of bearings with the spacer.

 

But you cannot just move all the guts back and forth between an M94 and M97 case because the M94 intermediate shaft rear bearing is different than the M97, so if you need to replace the case then you're either going to have to find an M94 case or find an M97 transmission. The latter will bolt right up to your bike so no issues there.