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Snapped-off bracket on swingarm - fixable?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Gromit, Aug 21, 2006.

  1. I just washed my bike after yesterday's expedition, and realised my chainguard was missing.

    Er, no - not missing, detatched and sitting atop the chain. I'd thought the bike was making a bit of a racket on the last leg home, but it was running fine and I was dog-tired so I didn't stop and look. :roll:

    Anyway, my first thought was that the mounting screws had shaken loose during the dirt road riding (taking my rego label with them). Then I noticed that the rear of the 2 mounting brackets for the chainguard had snapped clean off.

    Here's how the guard should sit:

    [img:750:563:ff2d6a4a49]http://img.photobucket.com/albums/v48/gromit/Bikepics/Chainguard1.jpg[/img:ff2d6a4a49]

    You can see where the rear bracket has snapped off:

    [img:750:563:ff2d6a4a49]http://img.photobucket.com/albums/v48/gromit/Bikepics/Chainguard2.jpg[/img:ff2d6a4a49]

    And here's a close-up:

    [img:750:563:ff2d6a4a49]http://img.photobucket.com/albums/v48/gromit/Bikepics/Chainguard3.jpg[/img:ff2d6a4a49]

    Any suggestions on the best way to fix this?


     
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  2. You'd have to get it welded. I wouldn't bother, just ride it around without the chain guard and use a chain lube that doesn't sling off.
     
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  3. It is an easy job to weld, any exhaust shop would be able to do it for you.

    Leave it off and risk a defect.
     
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  4. They can't defect you for not having a rear sprocket guard, only a front sprocket guard is required by law.
     
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  5. If its a steel swingarm easy to weld ie muffler man if its alloy you need access to an alloy welder (not so easy)

    Note need to disconnect battery REMOVE RECTIFIER/ RECTIFIER abd of course IGNITION MODULE

    Both of these can be fried by the high currents used in welding

    Just a gentle reminder as these can be expensive and i speak from experience
     
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  6. I wonder what Daryl Beattie might think of that suggestion. :wink:
     
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  7. I think this only applies to recreational registration - road registration requires a chainguard.
     
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  8. You sir may just be right!
    LOL @ Daryl Beatie comment.
     
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  9. I myself would be hesitant going to an exhaust shop. Not knocking them in any way -but the welding I have seen coming from most of them could best be described as utterly atrocious. Best you look for a small engineering workshop for satisfaction.
     
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  10. stick a magnet on the swingarm. if it's steel, i'll happily make you a new bracket for a six pack.

    also i've welded many bikes and cars (most late model with ECUs) without removing half the electrics. disconecting the earth and locating your work clamp close to the weld is fine.
     
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  11. Hey Gromit, find a good TIG welder, the swing arms are steel.Should take about 5min, very neat too.
     
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  12. Still have to be careful with putting the earth close to the work, if the earth isnt good it may try to find an earth some were else on the bike eg. paint, rust under clamp

    i also though the same until i weld the exhaust on a car then when i went to start the car the computer had been fried. wasn't until the other day when the electrician at work explained it to me. that i had relised what had happen, expensive lesson to learn just for the sake of removing earth lead from battery to protect electrics.
     
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  13. by "disconnecting the earth" i was referring to the battery on the vehicle
     
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  14. sorry N*A*M just read over that.

    steve
     
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  15. Welding the alloy swing arm is not the best idea unless it's a reputable place that works a lot with alloy welding, technicaly you are supposed to refer to manafactures recomendations.

    Just welding it back on, it aint so simple. The alloy more than likely (deffinately) needs a pre-heat (manafactures specs) before any welding. Welding can distort the swing arm through "heat shrinkage" and create"haz's" (heat affected zones) resulting in reduced strength and added stree's for that section.

    A decent shop will just heat the area a bit hotter than touchable, a quick weld and it should be fine. The alloy may require longer/slower cooling times.

    Bikes have gotten very high tech with exotic materials, each material has its preferances as to how it can be treated.

    As I seen posted, if it's not a legal requirement then leave it off.
     
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  16. Thanks - but as Jafu said, the swingarm's steel (I wandered out to the garage with a magnet anyway!).

    So hopefully it'll be a simple job for someone who knows how to wield a welder. I've sent N*A*M a PM. :)
     
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  17. I'm pretty certain that Suzuki would have used the chromolly sparingly in the production of the GSXF750 and gone down the more practical route, but good point all the same.

    Any muffler mob should be able to hit it with the mig and with a little silver touch-up and chain lube no one will be the wiser.
     
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  18. That swing arm does not look like a basic steel.

    Welding with a dis-similar steel aint the go, filler should be the same as the parent material.

    I don't work with bike frames, but I know welding and I can envision an apprentice stuffing up the job.

    It's just a little bracket, personaly I'd just apply a pre-heat before welding but find out what the swing-arms made of 1st.

    If you notice around the welding on the bikes, there is little to no heat discolouration around all welds.

    If an idiot does the welding for you and you get that discolouration around the weld, thats a "HAZ" and has altered the steels crystaline structure to lose uniformity.

    Heat distortion over a short length will be minimal in any case, I just like things done right the 1st time.

    Just mig weld it on and chances are you will never have a problem.

    Last point, it's hard to see if any material was ripped out of the swing arm itself or if a cold weld just peeled off the top. Damage there must be repaired correctly or it WILL result in crack/failure.
     
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  19. Thanks, saintan. :)

    There doesn't appear to be any damage to the swingarm itself, thankfully. I'll proceed with caution - and certainly not without confirming what the swingarm's made from.
     
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  20. I agree what what's above. That swing arm, even if it's boring old steel, will be heat treated for tempering for sure I'd say. A competent Tig welder is teh safest bet as Tig welding will keep the heated area small.
    A good welder may even gas weld it, and slowly allow the area to cool using the flame to bring it down in tepmerature.
    Considering teh critical nature of a swing arm, and the torsional loads on these one sided swing arms. I would use a professional.
    The fact the original weld broke could also be a sign the entire structure was tempered after welding.

    Regards, Andrew.
     
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