Cracked swing-arm?

[Mike.Gayner]

Did you say it's in a GSX750F? The one we have here has a steel arm in it.

Nope GSX-750W or Y depending who you ask. Quite different from the F. See the picture I posted back here: http://i.imgur.com/L9xPLKg.jpg

[Crasherfromwayback]

Nope GSX-750W or Y depending who you ask. Quite different from the F. See the picture I posted back here: http://i.imgur.com/L9xPLKg.jpg

Ah...yep. I like them much betttera.

[Mike.Gayner]

Showed the pictures to a mechanical engineering friend with some experience in materials - he reckons damage caused by crushing (e.g. overtightening with the spacer missing) is unlikely - it would cause permanent deformation and there would be other obvious signs like bruising. He says "If those fibers had enough stress in them to start a crack, it should have formed at the weld across them at the shock mount".

He also says "An extrusion defect seems the most likely as they are typically longitudinal however even that is unlikely.", and he's otherwise perplexed like everyone else.

My best guess at this point is a manufacturing defect that has eventually resulted in the crack. But I'm no engineer.

edit: Another guy made this little model using what little information he could extract from the picture. http://i.imgur.com/PXiYOZQ.jpg

[bogan]

Showed the pictures to a mechanical engineering friend with some experience in materials - he reckons damage caused by crushing (e.g. overtightening with the spacer missing) is unlikely - it would cause permanent deformation and there would be other obvious signs like bruising. He says "If those fibers had enough stress in them to start a crack, it should have formed at the weld across them at the shock mount".

He also says "An extrusion defect seems the most likely as they are typically longitudinal however even that is unlikely.", and he's otherwise perplexed like everyone else.

My best guess at this point is a manufacturing defect that has eventually resulted in the crack. But I'm no engineer.

edit: Another guy made this little model using what little information he could extract from the picture. http://i.imgur.com/PXiYOZQ.jpg

Yeh, you'd have to be a particularly ham-fisted operator to smush a swingarm of the size wall, even then, and like he said, you'd get other signs too. Have you had a good look around for stress raisers (tight radius bits, chips and deep gouges etc) along the crack on the inside?

[Mike.Gayner]

Yeh, you'd have to be a particularly ham-fisted operator to smush a swingarm of the size wall, even then, and like he said, you'd get other signs too. Have you had a good look around for stress raisers (tight radius bits, chips and deep gouges etc) along the crack on the inside?

Nothing obvious that I can see, but the truth is I really don't know what I'm looking for. I havent had the axle out yet though. This is all I can see at the moment. http://imgur.com/I6WuwcR.jpg

[manxkiwi]

I'm still going with the no spacer option. Tell you what, when you drop out the wheel, re-assemble without the spacer and give it a wee nip. I'll wager the crack will open and flex back when you back it off.

[imdying]

I'm with you. I'm no engineer and having nothing technical to go on, but I have found that with Japanese motorcycles, failures seem to be more often than not boiled down to some sort of human error. If it were an old British bike, or an Italian bike, just crapping out because of defective parts would be much easier to swallow.

[bogan]

Nothing obvious that I can see, but the truth is I really don't know what I'm looking for. I havent had the axle out yet though. This is all I can see at the moment. http://imgur.com/I6WuwcR.jpg

Too hard to see anything like that in camera pics from that angle I'm afraid... Once the axle is out, might be worth doing a good comparison between the two sides.

[Drew]

Chuck it out, and graft a Gixxer thou swingarm in the thing.

[Mike.Gayner]

Chuck it out, and graft a Gixxer thou swingarm in the thing.

That would be a mission considering this bike is set up as a twin shock.

edit: type-o

[Flip]

I suspect it cracked because the axle bolt was not done up tight enough. Its an aluminium extrusion so its perfectly weldable. Do check that the correct spacers are in the wheel.

I would however get it done by a qualified welder, not a bike mechanic, student welder or some body who works for a welding supplier. Just pull the swing arm out so there is no chance any stray earth currents don't fuck your electronics.

What the fuck do I know about welding anyway.

[Drew]

That would be a mission consider this bike is set up as a twin shock.

edit: type-o

Yip, that'd make life difficult. My bad.

[ducatilover]

What the fuck do I know about welding anyway.

You ride a Harley, so...



I still stand by no axle slide being in.
I reckon a decent rattle gun will do similar shit though?

[Mike.Gayner]

Found a used replacement swingarm for $150. Sorted.

[Mike.Gayner]

Received used replacement in the post today - this one also has a crack in it. This time on the inside non-drive side. Not sure whether to be pissed at the wrecker, Suzuki or both.

http://imgur.com/xbK42Ou.jpg