Driveshaft: caught just in time

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hools100RS
Posts: 73
Joined: Thu Aug 19, 2010 7:43 pm
Location: Central Goldfields, Victoria, AUS.

Driveshaft: caught just in time

Post by hools100RS » Wed Aug 16, 2017 2:58 am

My old ‘81 r80g/s is a pearler. Oct. 1980 build. In its 350,000 k lifetime, it’s on its third set of rings, has had cam chains, rotors, diode boards, regulator, diff bearings, exhaust headers (the originals went porus!) broken spokes, bent handlebars, flogged needle jets, valve guides, clutch plate……. all replaced or repaired, and they’re the things I can remember!! As part of its service it has towed trailers, survived outback wildlife collisions, buried itself in the side of a Ford Festiva. It has suffered innumerable crashes and drops all of which have added to the patina of scars and scrapes (a bit like its owner!)…..badges of honour. It has saved my life on several occasions…….it has never failed to get me home. I’ve had some great bikes over the years but the g/s is without doubt the one I‘m fondest of. God, it’s enough to bring a tear to a glass eye!!
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On returning from a rally at Strathmerton on the Murray River several months ago, the rear end developed…..I dunno…..like an intermittent metallic whine……my immediate thought was diff bearings. On the centre stand, roadside examination showed no noticeable binding or metal on the magnetic plug……no grinding…..I decided to go for home and once home, laid the bike up until I was able to examine it in more detail. That was last weekend!
The g/s (>1980) of course has the shock absorbing drive shaft, complete with torsion ramps, diff coupling and circlip all held under tension with a hefty spring.
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courtesy: Joerg.
On checking a spare diff with drive shaft in situ, there is no rotational movement and essentially no compression that can be achieved without a tool to compress said spring to enable the circlip to be removed and the shaft disassembled from the swing arm. Still with me?
I had replaced the uni 45k ago and because restaking the replacement wasn’t an option, had washers tack welded into the yoke openings to locate and prevent the new joint from any lateral movement. Me 109 knows where I’m at!(The next replacement will be with washers and circlips!) anyhoo…… The universal joint, just peeking out of the gearbox end of the swing arm, seemed to rotate smoothly enough in both planes.
On closer inspection a washer was missing and the uni cup on one of the yoke arms had migrated to flush with the yoke surface and only prevented from further movement ( and catastrophe!!) by the tiniest weld remnant from the original tack. I relocated the cup and retacked the washer, which I eventually found trapped in a fold of the swingarm bellows!
With the compressor tool I was able to compress the shaft to release the circlip holding the whole lot together but something was strange in that the whole setup was wobbly and kind of loose! (unlike my spare). The reason of course being a broken driveshaft torsion spring.
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The culprit!
Fortunately I had a spare in a bucket of diff and driveline bits and it went back together with minimal problems.
I didn’t take any pics as my mission was repair and not documentation, sorry, but I thought someone out there would be interested…..maybe experiencing similar. With the high km’s, the pretty good condition of the other components and the straightforward fix……I’m not complaining.
What could cause a failure like this in the first place? Overloading, too much weight?........sudden jerky starts?.......miles of corrugations?.......landing off little jumps?........or maybe a combination of all of these? More importantly, other than the uni disintegrating what would the repercussions have been for me to have kept riding it?
Anyway the g/s lives to fight another day. Like grandads old axe, it has had many replacement parts and has been in a state of constant refinement but is still pretty true to the original. It has given me and one other previous owner, incredible service. hools.

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ME 109
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Location: Albury, Australia

Re: Driveshaft: caught just in time

Post by ME 109 » Wed Aug 16, 2017 4:46 am

Hey hools, busted spring is not ideal but as you found it got you home.
Not sure if the broken spring can hit the swingarm tube anywhere? If not then I'd say just a clunky roll on/off as there would plenty of slop with the two drive gears not held together by the spring.

Welding school for you! I got 15 years out of my first uni fix.
Still on the second repair but I reckon my coupling is just about flogged out and no longer delivers the cush, so to speak. I use the clutch to feather the roll on/off which basically eliminates it.

I think your spring suffered from fatigue. One lucky full compression broke it.
The spring itself could have had a minor surface or internal defect that grew over time.
Studying the break in fine detail would show the cause. If we knew what to look for, exactly.
Lord of the Bings

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hools100RS
Posts: 73
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Location: Central Goldfields, Victoria, AUS.

Re: Driveshaft: caught just in time

Post by hools100RS » Wed Aug 16, 2017 6:01 am

G'day Jeff! Yes...good call...I'm a crap welder!! But there must be significant stresses on that yoke as some of the other welds had the beginning of fractures across them which I had to repair. Still, I can't get over the 'repairabilty' of so much that I've been able to break over the years and the toughness of the base article.These airheads are an amalgam of simple, strong engineering, wonderful performance and tremendous character......is it any wonder we get tempted to explore the limits of what they can do. Only airhead owners/riders get it!

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ME 109
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Re: Driveshaft: caught just in time

Post by ME 109 » Wed Aug 16, 2017 6:36 am

hools100RS wrote:
Wed Aug 16, 2017 6:01 am
Still, I can't get over the 'repairabilty' of so much that I've been able to break over the years and the toughness of the base article.These airheads are an amalgam of simple, strong engineering, wonderful performance and tremendous character......is it any wonder we get tempted to explore the limits of what they can do. Only airhead owners/riders get it!
Reckon you're pretty spot on there.
Lord of the Bings

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Rob
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Joined: Thu Feb 13, 2014 2:05 am

Re: Driveshaft: caught just in time

Post by Rob » Wed Aug 16, 2017 12:14 pm

hools100RS wrote:
Wed Aug 16, 2017 2:58 am
...It has suffered innumerable crashes and drops all of which have added to the patina of scars and scrapes (a bit like its owner!)…..badges of honour. It has saved my life on several occasions…….it has never failed to get me home. I’ve had some great bikes over the years but the g/s is without doubt the one I‘m fondest of. God, it’s enough to bring a tear to a glass eye!!
Image

Did you ever get to meet Bill Emory of Perth?
I'm not sure if his tear duct on that side was intact, or not.
Rob V

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Zombie Master
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Location: Vancouver Island BC Canada

Re: Driveshaft: caught just in time

Post by Zombie Master » Wed Aug 16, 2017 2:04 pm

Heart warming story! A very good bike! I remember that the angle of the swing arm in that GS causes the universal joint to be at a less that optimum running angle. Could that, over time have caused the break?
Any and all disclaimers may apply

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SteveD
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Joined: Tue Aug 03, 2010 3:29 am
Location: Melbourne, Oz.

Re: Driveshaft: caught just in time

Post by SteveD » Thu Aug 17, 2017 4:51 am

Bill huh! His anniversary was August. How many years?
Cheers, Steve
Victoria, S.E.Oz.


1982 R100RSR100RS supergallery. https://boxerboy81.smugmug.com/
2006 K1200R.

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