"clunk" in driveshaft on overrun

[Bob_Roller]

With the swing arm removed, the transmission comes right out after removing the attach fasteners .

[Ed Miller]

Yes, you should be able to remove the gear box to the rear with the air box removed.  To be on the safe side I like to remove the clutch lever and throwout bearing stuff there at the back, so I don't whack it into anything.  

[Bob_Roller]

I forgot about the clutch arm, also, if the pushrod for the clutch, doesn't want to come out easily, it's got a hole drilled in the end, and it's threaded, so if you can find a small screw to thread in there, it might make removal easier .

[nhmaf]

Go to the R65 Wiki section of this forum, under Repair->Transmission->Clutch Replacement and that should give you all the info you need to remove the gearbox, without having to move the engine - or completely removing the swingarm (which you've already done anyhow..

A couple bolts in the front of the airbox bolt through into the rear of the engine casing, so it's gotta come off (see pictures).  Also, DO NOT MESS WITH THE SMALL PHILIPS HEAD SCREW THAT YOU WILL SEE IN THE TOP/MIDDLE of the gearbox (revealed when airbox is removed).  It is holding a metal plate inside the transmission, and if you remove the screw, the plate can become dislodged, and requires a complete dismantle of the gearbox to refit it (very $$ if you otherwise don't have to crack open the gearbox).

Best of luck with the investigation.   IT may be that the output shaft bearing is going, which would be a not-too costly repair.   There is however, an internal shaft with lobes (like a similar version of what itoward the back end of the drive shaft in the swingarm.   It isn't very common, but not unheard of, for one of the lobes/ears on the mated internal shaft to break.   I am hoping that this isn't the case with yours, but it is starting to sound a little familiar to a another case that I have heard about.   Fingers are crossed for you..

[oldbiker]

Thanks Bob and nhmaf. I have the gearbox removed and did`nt have to move the engine. I fabricated a puller to remove the flange and by God it was tight. I have examined all the bearings  and gears in the box. The only wear I see is at the end of the splined shaft. The helical gear there and it`s mate obviously were stressed though no serious wear. The lobes on the cush drive are intact but there are visible signs that the lobes were slapping. Is it possible that that the spring may have weakened or shortened? Could this be the origin of my "clunk"? I will replace the output shaft bearing. I have looked at Wiki 65 and found it very helpful. I will have to sit and study it for a while before I do anymore work. Honestly I was`nt aware that there is so much information on this site. I am just getting familiar with computers and am a bit nervous about pressing buttons like opening gearboxes. I am going to try and attach a photo of the output shaft. The length of the spring between the restraining flanges is 38.87mm. Is this correct?
Thanks again for the advice. I am away to Spain for a week to enjoy the weather and the wine. I always envy them being able to bike all year round. I hope I will remember how to put all the parts together again.

[nhmaf]

You certainly do dive in though once you've a mind to do so !

Do take LOTS of pics.   I (and others as well) also have a love of small plastic zippered sandwhich/food storage bags for putting parts in.  I will put the small bits that go together for each subassembly, or maybe left side .vs. right side, etc. and label as such so that I don't end up with any extra parts at the end of re-assembly.

The "clunk" *might* be coming from that assembly you have there - the spring loaded lobes are supposed to help deal with the changing shaft loads/torque reversals in a semi-graceful manner.   I seem to think that the spring is supposed to be a bit longer than it appears to be in your photo, but I could be wrong/"mis-remembering" and haven't taken gearbox apart in long while.   Justin B may chime in as I recall he had one of his bike's gearbox apart early this year and may have more recent info to offer in this regard.   Before you took the shaft out, was there much "end-play" (Ability to push/pull breabox shaft in&out along its axis ?

A week in temperate Spain sounds lovely - I think we should all be so lucky!   Enjoy!!!

[oldbiker]

Hi nhmaf
I have explored a little more and dismantled the input shaft.  The thrust spring now measures 44.6mm when relaxed. I notice that the ears on the thrust block are scarred and worn. The seem to have worn into the edge of the spur gear. I took a photo but it is not very clear. The spur gear splines or teeth are about 1.3mm shorter where the ear of the thrust block was making contact. I feel that the ears of the thrust block were "riding"over the ears of the spur gear causing the "clunk".

[Bob_Roller]

I checked the BMW shop manual, and couldn't find a nominal dimension for the spring .

[oldbiker]

Hi again
I think I pressed a funny key on the computer sending my note before I was finished. I also found compacted aluminium powder in the splines under the thrust block. It was there a long time    and had not contaminated the oil. I imagine it was there from a previous mishap as I notice the inside of the housing suffered trauma in the past  but causing no problems now and this swarf could not be removed till the input shaft was dismantled. I am keen to know how those ears and spring ar e supposed to operate.
Thanks again for all the help.

[Bob_Roller]

I think the theory of it's operation, is to allow a bit of relative movement when a shift is made, takes the jolt out of the drive train .

I've been told that if you ride a bike without the 'cush drive' it becomes quite apparent during shifting .

[oldbiker]

Hello everyone
Back from Spain where the weather was lovely and the wine enjoyable. Here at home we have just had our old Celtic feast of Oíche Shamhna or Haloween when the ancient Celts felt that the light in the world was gone. Our hours of daylight will get progressively shorter until the Winter E solstice. There is an ancient passage tomb in Newgrange Co Meath, 3200 yrs,  where the rising sun shines in the top along a passage to an inner chamber for about 15 mins. From the on the days get longer culminating in the fertility feast in May of Lá Bealtaine. Anyway I hope my work over the Winter will be fertile and reproduce a smooth gearchanging BMW R65LS.
I have ordered a set of seals ,bearings, gasket and the helical gear and drive with the "lobes" . I have done a lot of reading on assembling the gearbox and tranny and have a few queries-:
Can I bolt the final drive to driveshaft before I attach flange to an already fitted gearbox?
What is the best method to ensure that the drive shaft  or flange are not rubbing off the housing?
Is the swinging arm the last to be set and torqued?
Is this done by removing the sparkplugs and turning the wheel while in gear?
Thanks again for the advice
Oldbiker