Transmission removal method

[tunnelrider]

Hi good people of the forum, hope all is well. I've been able to not post any questions for a number of years now, while keeping an eye on the forum occasionally, and it's great to see the input is still going strong.

I've got noisy transmission (gearbox) output shaft bearings, a little bit surprisingly only 45,000 km since I put new bearings on all the shafts.

I removed my 1985 gearbox unit last time following the Clymer manual method of moving the engine and gearbox forward before unbolting the gearbox from the engine case and taking the gearbox out, leaving the swingarm in place. Although fairly straightforward to do, I found this method a little awkward, leaving the engine on wooden blocks for a month while I serviced the gearbox.

The Clymer manual has a different method of gearbox removal between years of manufacture.  For 1970 - 1980 models it tells to move the swing arm back to remove the gearbox, while for 1981 models on it tells to move the engine forward.  Does anybody have an inkling to why the different methods?  Something to do with the flywheel on earlier models vs clutch carrier of later models?

Thanks for any tips,
Dan

[georgesgiralt]

Hi !
On my sole BMW, an '82 R65, I removed the gearbox quite often (to repaint the frame, to repair a broken spring in the selection pawl, and so on...) I've followed both methods, either removing the swing arm or moving the engine.
I tend to prefer moving the engine because putting the swing arm back and adjusting it is not that easy. Add to this that tapered roller left open can gather dust and impurities and die of that...
On the contrary, moving the engine does not involve removing difficult parts (like headers) or anything else...
But of course YMMV ....

[skyblu79]

I agree with georgesgiralt, I also tend to prefer moving the engine because putting the swingarm back and adjusting it is not that easy.

[tunnelrider]

Hey georgesgiralt, nice to hear from you again.

Thanks for your replies georgesgiralt and skyblu79, and your experiences doing the removal both ways. 

Definitely sounds like moving the engine forward is the easier and preferred method of the two.  But perhaps it's time I looked at the swingarm anyway?

The swingarm is one of the areas I've mostly left alone in 10 years of having the bike, aside from giving it a grease gun squeeze once every few years (which usually squeezes out straight away) and more frequent oil changes.  I've felt a bit guilty of neglecting the swingarm, especially since I've taken the bike through numerous streams and small rivers over the years, and haven't ever inspected the swingarm bearings.

What are the symptoms if the swingarm's not right?  I guess if the bearings are seized it would be reasonably hard to tell? If the swing arm preload is too loose, would the handling would be unsteady?  I can't say I've noticed any handling problems, hence haven't gone into the swingarm, but gradual worsening may go unnoticed.

Would anybody agree it might be time I took the swingarm off, since it's a way of getting the gearbox out anyway?

Cheers

[georgesgiralt]

Well, testing the swing arm bearings is the same as the steering one.
Remove the two shock and (without the rear wheel ) move it up and down. If you feel any stopping or resistance, you know the answer...
Same for the play. Grab one arm of it and pull/push on it. If it moves even the slightest, you know the answer.
Setting the preload is easier than on the steering as it is done by setting the torque as per specifications and then backing up per proper procedure.

[tunnelrider]

Ahh yeah, of course. Take the shocks and wheel off, have a play! Thanks for the tips and explaining georges, good sense to check before taking the plunge. I'll post back on what I find.

On another note, am I right to be disappointed with only 45,000km on new gearbox output shaft bearings?  I'm not a particularly sympathetic or gentle rider so that may explain the wear, but I think that's not totally plausible if BMW trust the same gearbox to serve 1000cc bikes?

[Bob_Roller]

I've always used the swingarm removal when removing the transmission.
One thing I found, is the socket I was using to remove the jamnut on the pin that swingarm rides on .
The standard depth socket was too wide to down to the nut .
I had a deep well socket and it just barely fit .

[georgesgiralt]

I've had a standard socket machined to remove the chamfer in order for it to grab the nut properly, and reduced the external diameter on a lathe for it to go easily into the swing arm recess..
As I had to pay for the machining, it was an expensive socket and I keep it well buried into my drawer !
If you buy a very high quality socket, you'll find that the walls are thinner than cheap ones. But the steel will be harder so more difficult to remove the chamfer... And if you use a grinding tool to do so, be really slow and cool the socket very very often in order to keep the hardening .....

[Burt]

I've had a standard socket machined to remove the chamfer in order for it to grab the nut properly, and reduced the external diameter on a lathe for it to go easily into the swing arm recess..

That is exactly what I did as well.  That socket is dedicated to one job only and I turned it up when I had access to the required machinery. 

I have a few tools dedicated to single jobs and they are invaluable when needed.  Recently when I asked you about the Polish stanchions you purchased I sent them an enquiry and they never replied, so I am transferring a complete front end off one K75 to another as it is a time critical job.  I needed a 24" monkey wrench to undo the tensioning nut on the steering head, so borrowed one of a mate.  The next day I went and bought one for myself. Fortunately a lot of the simple specialised tools that are required for BMWs are available as aftermarket options. 

I have bikes in the F, K & R ranges and I am fortunate that I have access to a large community of BMW riders locally. 

[tunnelrider]

Sorry about the lack of action on checking the aswingarm, I had a breakdown last weekend on another previous repair  , 40K km ago since I "repaired it" and got the heads all new valve guides, valve seats and valves fitted at an engine shop.

I had a look today and the left exhaust valve is stuck in the valve guide, maybe bent.I'll  have to sanpaper off the edges esp. on top of the stem before trying to take it out.

Funny how things cycle 'round again. I last did these 8-10 years ago,  gearbox and heads. 

 

[tunnelrider]

Ive been running a worn dimpled rocker arm on that valve for a while, was a bit noisy beforehand.

 No dimples, flat surface on a rocker arm please!  Yessir

 

[georgesgiralt]

Sorry about the lack of action on checking the aswingarm, I had a breakdown last weekend on another previous repair  , 40K km ago since I "repaired it" and got the heads all new valve guides, valve seats and valves fitted at an engine shop.

I had a look today and the left exhaust valve is stuck in the valve guide, maybe bent.I'll  have to sanpaper off the edges esp. on top of the stem before trying to take it out.

Funny how things cycle 'round again. I last did these 8-10 years ago,  gearbox and heads. 

 

Seized on the guide ? Lack of oil ? Wrong guide material ?

[tunnelrider]

Not 100% sure what's caused the exhaust valve to bind yet.  I haven't had time to try and take it out yet.  Here are some pics.

The valve doesn't look properly seated on the valve seat.
The rocker arm is a little notchy.  Could this cause the valve stem to bend possibly?

I've also heard about valves 'microwelding' to the valve seats at high rpm - maybe this has something to do with it?  I've had some rides over the past few years with sustained riding round 7000rpm for 10-15 min stretches. I know, I know... unsympathetic for sure. 

[georgesgiralt]

Did you clean the heads ? Because they look too dry to me...
The valve look bent and has suffered severe wear on the end stem. (this part is specially treated to be diamond hard, so using it implies very harsh treatment...)
My bet is to drive the valve and the valve guide out (with the valve still installed) and check the seat then either look for a new head or put a new guide and valve.
Job for a proper equipped mechanic with knowledge of what to do/how to do it...

[tunnelrider]

Yes the head and rocker arm were wiped clean of oil before taking the pics.  I agree the tip of the valve stem shows some harsh treatment, and I know the rocker arm pad for pushing that valve wasn't in the best shape.  Seems new rocker arms are becoming scarce and expensive on line, as demand for them increases I guess.

I've got a spare set of 1980 heads with the older type rocker arm without the plastic bush, that has a different, larger pad where it pushes down the valve stem than the later style (post 1985?) rocker arm.  I've tried fitting it on the 1985 head to get rid of that worn left exhaust rocker before, but with it's larger push pad I recall there was barely any adjustment left on the adjuster nut for adjusting valve lash.

I'll probably use the spare 1980 heads and rockers if I get to the point of being ready for the road but haven't fixed the problematic valve and found a new rocker arm by then.