The BMW GS boxer twin thread

[Padmei]

Yes I saw those on Stagehands thread. As you know he's been offered a Paul Rooney bike to ride on the Safari.

Myself I don't really like them - I don't really like the crashbars either. I've heard of the crash bars twisting frames etc but they don't hide that beautiful engine. I reckon a better looking alternative would be a type of blade running lengthways down the head. No not like Grease or Ben Hur - the other way

[Box'a'bits]

Yes I saw those on Stagehands thread. As you know he's been offered a Paul Rooney bike to ride on the Safari.

Myself I don't really like them - I don't really like the crashbars either. I've heard of the crash bars twisting frames etc but they don't hide that beautiful engine.

I think that they look practical for bikes that are more ADV oriented. In practice I don't think they'll be that visible (after all they are under the barrels). They look to offer better protection for twin plugs (if that is of concern). & they will be less obtrusive on 4wd tracks, where the crashbars hang up in ruts. Have a look at the slideshow in the link. More pictures of your favourite orange framed R65

[Pampera]

Source of the glittery flakes was a disintegrating bearing race, sludge is the rest of the bearing and the noise was the preceeding having their entropy reduced. Gearbox bearing very close to complete failure with gearbox break up almost inevitable if it had.

Motobins are out of stock of bearing kits for weeks (months?) so the R80GS is proving about as useful as the 2007 Dakar it replaced!

Motobins order arrived after a week delayed by Customs, gearbox was rebuilt and I started installing it on Friday night. Driveline was completely reinstalled Saturday afternoon but with the bike on the centrestand turning the rear wheel revealed the gut wrenching sound of something in the driveline graunching and fouling every few cm of turning. Any load on the swing arm upwards - even just upwards force exerted by hand - and the wheel turned freely. Talk about frustrated, angry and demoralised. This was meant to be going back to dependable basics after 4 years of the electrical disaster that is a modern EFI BMW.

To cut a long story short, eventual result was dismantling again (this time including the final drive end of the assembly as well) to reveal the driveshaft attach nuts were fouling the front lower lip of the driveshaft tube (swingarm tube). Checking everything and careful reassembly delivered the same result. I could not see anything I had done wrong. Had a visit from Mike D tonight and he confirmed the same.

All was as expected. The only cause for the symptoms could be that the shock is a touch too long (or the Paralever arm a touch too short). Causes I discounted in favour of a mistake by me during reassembly. The Paralever was not removed from the bike and unlikely to be different. However after checking everything Mike noted that the damper had evidence of slight damage and that entry had been made into it (rebuild of sealed damper). Most significantly, with no preload the spring was loose enough to turn, suggesting the stops had settled or been damaged. The cause can only be the shock is mm too long, dropping the end of the shaft down slightly below its normal full extension (Paralever tips final drive down at its front multiplying the effect) and bringing the gearbox - shaft flange nuts into contact with the inside lower front of the swing arm tube.

Picture shows the over tilted geometry that results (it is the far end that fouls).

Mike is lending me a standard shock to check this, the factory manual does not specify eye-eye length for the damper/spring assembly.

Helps my morale knowing it was not me, but talk about discouraging.

I like the Paralever even less than before. The shaft end of the front rubber bellows (the poorly shaped Morobins one) is a bear to install and there was a whole lot of other rubbish to strip and reassemble at the final drive end. I was luckly (and used some tricks) to get the spline to re-engage (was checking I had not displaced it and caused the problem) but on the earlier models apparently this can reduce a professional mechanic to "walking away for a rest". Monolever rules! I just rode carefully to keep the bike attitude level. In return no universal joint wear, a simple rubber boot that almost installs itself and a drive that lasts the life of the bike without anything but occasional oil changes! Yes I am a Luddite (now).

Anyway, this suggests that a damper/spring a touch longer than standard could be very dangerous in view of the obviously tiny standard clearances inside the shaft tube on full extension. Watch it.
Michael

[Padmei]

Hmm interesting. I just went out & measured 3 of my shocks. They are all 495mm eye to eye. What's yours?
My final drive looks as goofy as yours on the centre stand.
I have cursed many times trying to get the front gaiter back on. I now take out the battery box, shock etc & tie the driveline up with a tiuedown level. They go on a piece of wees now with a bit of even breathing.

The airheads can be a bit of as bugger getting them back to newish. I had a similar experience after putting my gearbox back together to find a major oil leak out of the rear seal. A pita at the time but work thru it you'll love it when it starts to deliver the miles back to you. They were prob as annoying back when they were new but modern (carbed & basic ) bikes are more user friendly.

[Pampera]

Hmm interesting. I just went out & measured 3 of my shocks. They are all 495mm eye to eye. What's yours?
I have cursed many times trying to get the front gaiter back on. I now take out the battery box, shock etc & tie the driveline up with a tiuedown level. They go on a piece of wees now with a bit of even breathing.

A pita at the time but work thru it you'll love it when it starts to deliver the miles back to you. They were prob as annoying back when they were new but modern (carbed & basic ) bikes are more user friendly.

Hard to measure accurately without some sort of table set up but 502 - 503.5 so far as I can see. Less than half of that 8 mm difference is more than enough to eliminate the fouling. Thanks.

I didn't even contemplate putting the oblong shaft end of the bellows on in situ. It got fitted with the shaft off the bike and was a struggle even with this. The round gearbox end slides right on with a little vaseline with the swingarm in the right place. Part of the problem is the rubbish Motobins pattern part though - it does not match the shape of the BMW part. I am going to measure up their gearbox flange bolts carefully - I would not be surprised if they are a crucial 0.5 mm out in the wrong place also. There is often a reason genuine costs more.

I HAD a perfect airhead (1992 RS), albeit I rescued it from tetering on the edge of the slide to POS, and now am regreting selling it (last month) in favour of this GS. After four years of modern BMW ruined trips I just wanted a bike I could rely on to take Debbie on Adventure rides again. My resilence was worn through 2 years ago!

Forgot to record the reason for the bearing failure - it was the circlip problem, letting the bearing move. On my 89 RS the gear return spring broke at 90,000 km and I got the circlip mod and all new bearings before it happened. GS bearing was worst Mike had ever seen - one step away from complete failure and gearbox break up. So worn there was no feel of "grittiness" left, only air rubbing against air!

Michael

[igormortis]

Interesting. Makes me wonder what tricks are going on here:



The relocated shock mount and shorter torque arm are the most obvious - but your experience would say that some trickery is still needed to avoid gearbox flange to swing arm contact.

[Padmei]

Pah that's photoshopped. look how short the muffler is & the size of the blue exhaust pipe running to it.
Maybe the shortened torque bar just keeps the final drive on that angle so the ride height is increased. I don't think you'd have more travel than a standard para due to the limitations of the UJ but you'd be missing more rocks etc.

[Pampera]

Interesting. Makes me wonder what tricks are going on here:

[]

The relocated shock mount and shorter torque arm are the most obvious - but your experience would say that some trickery is still needed to avoid gearbox flange to swing arm contact.

Something as simple as reducing the size of the flange securing bolt heads (grinding them down for us NZers) would provide extra useable travel at the wheel end of the assembly. I guess the front end of the swingarm tube could also be relieved (cut away for us NZers) and a custom extended rubber boot used to cover over the hole for even more travel.
Michael

[Pampera]

[QUOTE=Pampera;1130295256]Hard to measure accurately without some sort of table set up but 502 - 503.5 so far as I can see. Less than half of that 8 mm difference is more than enough to eliminate the fouling. Thanks.

QUOTE]

After a day of consideration I have decided that a professional approach is required for such a critical component. A ratchet tiedown, suitably tightened, will now form a permanent part of my rear damper/spring assembly so as to deliver the correct no load ride height. However, I am thinking of checking this decision with the UK GS online community first. What do you guys think?

Michael

[Padmei]

You're onto something there Michael. i reckon there's money to be had if you decide to make a few of them. What about cutting the shaft a bit then welding a lump inside so it won't drop anymore.

I have 2 rooted shocs here you could grab bits out of if you wish.

[NordieBoy]

You're onto something there Michael. i reckon there's money to be had if you decide to make a few of them. What about cutting the shaft a bit then welding a lump inside so it won't drop anymore.

I have 2 rooted shocs here you could grab bits out of if you wish.

You just put a small spacer on the shaft below the piston.
The Nordie had a 5mm one which, when removed, raised the back end 25mm.

[BMWST?]

You just put a small spacer on the shaft below the piston.
The Nordie had a 5mm one which, when removed, raised the back end 25mm.

i have a completley (or nearly completely) oilless rear shock with std spring here too.

[_Shrek_]

[Pampera]

Motobins order arrived after a week delayed by Customs, gearbox was rebuilt and I started installing it on Friday night. Driveline was completely reinstalled Saturday afternoon but with the bike on the centrestand turning the rear wheel revealed the gut wrenching sound of something in the driveline graunching and fouling every few cm of turning. Any load on the swing arm upwards - even just upwards force exerted by hand - and the wheel turned freely. Talk about frustrated, angry and demoralised. This was meant to be going back to dependable basics after 4 years of the electrical disaster that is a modern EFI BMW.

To cut a long story short, eventual result was dismantling again (this time including the final drive end of the assembly as well) to reveal the driveshaft attach nuts were fouling the front lower lip of the driveshaft tube (swingarm tube). Checking everything and careful reassembly delivered the same result. I could not see anything I had done wrong. Had a visit from Mike D tonight and he confirmed the same.

All was as expected. The only cause for the symptoms could be that the shock is a touch too long (or the Paralever arm a touch too short). Causes I discounted in favour of a mistake by me during reassembly. The Paralever was not removed from the bike and unlikely to be different. However after checking everything Mike noted that the damper had evidence of slight damage and that entry had been made into it (rebuild of sealed damper). Most significantly, with no preload the spring was loose enough to turn, suggesting the stops had settled or been damaged. The cause can only be the shock is mm too long, dropping the end of the shaft down slightly below its normal full extension (Paralever tips final drive down at its front multiplying the effect) and bringing the gearbox - shaft flange nuts into contact with the inside lower front of the swing arm tube.


Mike is lending me a standard shock to check this, the factory manual does not specify eye-eye length for the damper/spring assembly.

Helps my morale knowing it was not me, but talk about discouraging.


Anyway, this suggests that a damper/spring a touch longer than standard could be very dangerous in view of the obviously tiny standard clearances inside the shaft tube on full extension. Watch it.
Michael

Thought I had best post a follow up.
The OEM damper Mike loaned me was 8 mm shorter than the OEM unit removed from the bike. Fitted up with the bike reassembled the fouling above was removed.
Thanks to those who offered to loan me damper-spring units.
Reassembly was tackled in a very negative frame of mind. Not helped by third time trying to get the ill fitting bellow back on the shaft tube front, forgetting to put the fuel line under the air box before securing everything (not the first time I have done this) and pinging some strands when trying to reroute the right throttle cable (not misrouted by me) without stripping down my carefully balanced cable connections or disconnecting a worrying number of electrical thingees (technical term).
New cables ordered.
Motobins driveshaft bolts are actually fractionally smaller than the OEM examples so an even greater mystery - how on earth did the bike work before?
Be very careful out there - there is almost no safe clearance available in the event you use a non standard damper/spring.


Bike ran very well out to Martinborough and back on Saturday (160 km) aside from horn (relay ordered also) but it is going to take a while (without any issues) before I start feeling at all positive about this machine. Viva la my red Vespa!

Regards,
Michael

[Padmei]

I felt the same about venturing out withh Schmidt, now I feel more confident.
Give it time & your investment in time will pay off.