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  #1  
Old 7 Jul 2005
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R80 GS gearbox problems

Gearboxes on the aircooled boxer motors have really been given a bad repution, and unecasary so because they are so simple in design and are incredably robust.
Discussing a few problems that is the reason for their dimise, is firstly that it is importand to learn how to shift smoothly.
Even a very clunky box can be shifted with almost no resistance or niose if you keep the revs in the right place and with light presure on the gear shifter that will allow it to drop right into gear when the dogs are aligned.
Next, service the oil in the box when you do so for the motor witch should be at 4500 miles or 7500km, or not more than 6 months.
Changing more regularly will also reduce the amount of water colecting in the box.
Now the reason why water enter the box is by ways of the speedo cable.
When you look at the right side of the bike where the speedo cable enter the gearbox you will find a cone shapen rubber sealing of the cable as it enters the box.
This rubber is the problem as they start to grow hard and crack with age.
It cost approxematly 2$ and will take 10 min to replace. All you need to do is to use a 10mm spanner to undo the small bolt holding the earth cable from the battery. This bolt also hold the speedo cable in position. when it is completly removed you can pull out the speedo cable with the rubber crommet and a cylindrical plastic holder. By tugging hard you can pull the rubber grommet of, in most cases it will tear of. Fit the new one using some grease to help as it fits very tight.
Do not forget to replace the earth cable when refiting and make sure the recess in the plastic holder is turned toward the thread of the bolt.
The next will be the single biggest problem with these gearboxes. In 1982 BMW enginears decided to omit a small circlip on the front of the output shaft, directly opposite the drive shaft. This circlip has the very important job of holding a bearing in place on the shaft directly next to the helical 5th gear. Because of the helical design of this gear it exercise a lateral force onto the inner race of the bearing and ball tipe roller bearings are not desiged to take lateral forces, the bearing is bound to collapse after high milage. This causes tremendous damage to the fith gear, intermediate shaft and sometimes the output shaft and selector forks. These items being the most expensive parts in the gearbox.
It was only in 1996 after these models were allready taken of the market that BMW started to sell the output shaft in conjunction with the circlip.
To rectify the broblem you need to have the gearbox overhauled of coarse, sometimes you might be lucky and there is a croove in the outputshaft for the circlip but in most cases an engineering shop will have to cut one.
When the new bearing get fitted it is very importand to make sure the one from BMW, part no. 23 12 1 338 795, is fitted. This bearing is recently introduced has been changed to accomadate the circlip without a small wire clip, witch have a beter fit.( I have seen where even the circlip have been forced out of its groove by this presure from the fith gear.)
The BMW part is also more refined to give a longer live than stock bearings.
To check if your box is due for an overhaul you can place it on the centre stand and with the bike in gear with someone holding the clutch you can feel any roughness in the bearings by turning the rear wheel.
Bigger than normal metal particles on the magnetic drian plug is also a good indication of a worn bearing.
Last but not least, do not atempt this job yourself if you do not have all the special tools and a good manual, Haynes will not do as they do not explain how to set the endfloat of the shafts to well.
Check with your dealer that the right bearing go on the output shaft and most important the groove with its circlip behind it.
If this is done together with regular sevices you should do more than a 100 000 miles before the next overhaul.
It is important to change all seals and other bearings at the same time.
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  #2  
Old 8 Jul 2005
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Your experience is obviously the opposite of mine.

One problem with the BMW gearbox is getting the thing apart and back together when on the road, as this is an inevitablility.

The special puller tools are not in a regular garage, so its likely you will have to get them made as happenned to me in Russia. Ralphino Verde and myself have had a travelling set made so we can take them with us.

Output shaft flange puller and exhaust flange tool with a cut out and holes drilled to be used as a brace when loosening /tightening the output flange nut.

This is due to inevitable bearing or seal failure in the gearbox. His is a parot lever so the output shaft seal failure is more critical.

The Gearbox seems to last with small suspension travel twin shock rear ends, yet it seems to get beaten into a pulp by the G/S GS models. Just feel the shock going up a G/S drive shaft before re-attaching the output shaft to the drive shaft.

So having your schwinehundts gearbox rebuilt before you go is probably critical. But watch them do it because you might have to do it again soon!

Also BMW dont like you to use bolts twice, so expecting a gearbox or drive shaft out scenario remember to carry all those "one use " only bolts, selas and gaskets. If you have visa issues you wont be able to get them sent to you in time.

Good luck GSers and know that BOPS is with you.

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  #3  
Old 9 Jul 2005
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Simmo
Thats exactly what happend to Petze,a german traveller,taken out in Salta(northern Argentina) because of a rebelling gearbox,the bike was sent by truck to Javiers(Dakarmotos) repairshop in Buenos Aires.Of course a special tool for dissambly is being prepared!
Tour is running out in time,and should stay here for complete overhauling.
My old G/S never did any problems.I sold it back in germany with more then 280.000 done.
Are big diferences between the older and newer gs?
Thanks
KH
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Old 11 Jul 2005
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Acording the the Haynes manual

82 was when the helical cut changed to 17.5 degrees.

March 85 to april? 93 was the missing circlip problem.

I'd have though the missing circlip problem would be behind us by now - all those gearboxes would have been fixed.... ?

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  #5  
Old 13 Jul 2005
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Frank - not all redone by a long shot! Still plenty out there not had the shaft/groove solved.

Simmo, the NORM is for gearbox bearing failure to occur at somewhere over 60,000 miles/100,000km - mine (G/S) blew at around 150,000 km.

If a gearbox wasn't correctly rebuilt previously, it could easily fail much sooner. The bearing end float is CRITICAL. And the only "use-once" bolts are the 4 driveshaft to output spline bolts. Carrying a spare output, input, gearbox k/s shaft seal (if you have one) and gear lever seal is a good idea. Also a RMOS. I carried them all - and never used one.

------------
I just added the following to the original thread before noticing this, so thought I'd bung it in here too - may or may not add to gsworkshops excellent post above!

RE Gearbox

Simply changing the bearings (and while you're at it make sure you have the circlip, or get a machinist to machine it on the shaft for you) at around 60,000 miles / 100,000 km AND as noted making sure it's getting clean uncontaminated oil is normally sufficient.

In other words:

1. Make sure the speedo cable rubber boot is in good condition - this is where most of the water gets in - running down the speedo cable and past a perished boot.

2. Change the oil at factory intervals with factory recommended oil. Nothing else helps enough to matter imho.

3. REBUILD the gearbox at stated mileage above - all that's needed is to replace all the ball bearings - the roller bearing will easily go double that mileage, and is very expensive.

4. IF you have one of the gearboxes that doesn't have the circlip on the frontend of the output shaft, replace the shaft or get a machinist to machine a groove for the circlip into it.

5. Grease the input shaft spline at 20-30,000 mile /35-40,000 km intervals with the latest BMW recommended grease. NO need to pull the gearbox out, just pull it back a couple inches / 5cm, clean the splines on the shaft with a toothbrush wetted with a little gas or solvent, and then SPARINGLY coat the splines with grease - excess ends up on the clutch and ruins it.

That's really all that they need!

hope that helps...

Grant



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  #6  
Old 14 Jul 2005
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Hi,
I have the 93 circlip problem. The big bearing is broken. It was pushed from the 5th gear. I have the 93 version without the circlip groove. I want to put it in there. Has anyone pictures and technical details of how the groove for the circlip should be?

Thanks.

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  #7  
Old 14 Jul 2005
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Hi Uncle Charlie,

sorry, no picture. But I had mine done as well - the bearing was bust at 18.000 :-((

Wile you're at it, think about replacing at least the 1st gear by the lower geared version. I found it very useful to manoeuvre the heavy twin in critical terrain. I've fitted a short 1st and longer 5th plus ceramic clutch. Hope it lasts for the next 500.000 ;-)

Good luck.
Hans
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Old 15 Jul 2005
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Ed Korn at http://www.cycleworks.net/ in the USA will machine the groove for US$95.

Or any good machinist can do it if supplied with the shaft, circlip and bearing.

Grant

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  #9  
Old 15 Jul 2005
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I found a description how to make the groove for the circlip. Its in German but I think the picture is the important thing:
http://derdicke.de/mot/tools.html#welle

On the page is also the tool to disassemble the gearbox.

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  #10  
Old 15 Jul 2005
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That puller is much the same as the one we built.
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  #11  
Old 4 Aug 2005
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Once-use bolts on output shaft can safely be used a second or even third time (not recomended if you have acces to new ones. The biggist danger is crossthreading because the the thread pitch and size changes after every use.
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  #12  
Old 4 Aug 2005
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gsworkshop,
you wrote on an other post :
I have a english version of the original R80G/S workshop manual. If somoene is willing to host a site with this informatian or add it to thier site I can see if I can make a digital copy available.

sorry, i don t understand this "circlip" thing. where is it on your manual ?
otherwise, i m interested by your manual, wrote you a few times, but no reply.

or if you have any pic / reference somewhere for this "circlip" thing?
this may help you : http://flatmaniac.free.fr/ or http://flatmecanic.free.fr

i also had gearbox problems on my trip, with a r100gs paralever.

recently, i cheked a bit my clutch on my r80g/s monolever : change and adjust the cable properly, changed the little bearing on the top of the clutch lever behind the gearbox : it really makes a difference to have done those basic things, for the gearbox which is much smoother (up and down).

i put on the gearbox a special oil, which also makes the difference : kernite top blend sae 80w140.

happy trails

otherwise, i ve heard that you can buy reinforced stronger bearings than original but don t know where.

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Old 4 Aug 2005
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I have responded to Vincent's mail a few times maybe I have a problem with my subscriber. I will make the manual available in due time, but I need to make sure that it will be in good quality to download and print and still be legable.
The only bearing that give real problems is the one on the output shaft on the engine side. This is avialable from BMW as a harder bearing and made with special surface to rest against the circlip providing there is a groove on the shaft.
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Old 5 Aug 2005
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with pleasure :-)

if you could indicate also on the manual or elsewhere what this circlip thing etc ... looks like (i don t get it)

cheers
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  #15  
Old 5 Aug 2005
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See http://www.horizonsunlimited.com/tech/mcglossary.php for definition of circlip, and translations for many technical terms - unfortunately we don't have a translation for circlip, so if anyone can provide the various translations for circlip, post it here.

The circlip in question goes at the engine (front) end of the gearbox, on the output shaft. It goes in a groove which may - or may not - be there, about 1.5mm from the end of the shaft.


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