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Discussion Starter · #1 ·
I just received my aluminum swingarm in the mail (hooray!) for the 'ol 750.

The seller didnt mention some wear where the chain has mad a little contact with the swingarm. I think it's fine, but just for piece of mind I thought I would post here. The gouge is about 1-2mm deep.

Any input is appreciated! The third picture is the best.





 

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To me the second picture shows the worst damage, in the corner of the box area. I'd suggest taking it to a weld shop that does aluminum and have a bead welded across the gouge.
 

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Looks to me like someone tried to remove the chain with a grinder...
 

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Thats nothing to worry about at all. It's not all the way through, and more cosmetic then anything! I wouldnt worry about it.
 

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clean, install, ride.
 

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Discussion Starter · #6 ·
clean, install, ride.
Thats nothing to worry about at all. It's not all the way through, and more cosmetic then anything! I wouldnt worry about it.
Great news... a little annoying opening up the box to see that, but either way I trust it will be fine.
 

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It's a stress riser. If you don't want to weld it, at least smooth the sharpness that can cause a crack and polish it. Leave no sharp edges where cracks can form. The bottom of that scratch needs to be polished out. Maybe I'm paranoid, ok, yes, I'm paranoid, but I'd get it welded and polish it before it goes on the bike.
 

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It's a stress riser. If you don't want to weld it, at least smooth the sharpness that can cause a crack and polish it. Leave no sharp edges where cracks can form. The bottom of that scratch needs to be polished out. Maybe I'm paranoid, ok, yes, I'm paranoid, but I'd get it welded and polish it before it goes on the bike.
technically you are correct. it real terms: "ok, yes, I'm paranoid". That amount of damage, in that spot, will never crack. with a capitol V. The swingarm will break at the pivot pinch bolts long before the smallest crack will form at the gouge.
 

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The other place they (well, where mine went) crack is at the top, near the shock mount - close inspection is needed, because the crack starts as a literal 'hairline'. Mine failed close to the weld bead.

I'd do as duc96cr said - and at least smooth out the rough bits, and remove any sharp edges to the damage. Welding may not be necessary, but I'd consider it too. Just for peace of mind...
 

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I'm a paranoid guy as well and after my "mechanic" forgot to install the washer on my 900, well, needless to say I wasn't happy.

Aluminum is a tricky material, it has zero fatigue limit, meaning, it will inevitably fail at some point. I didn't feel comfortable with a repair job, since now you have a section of your swingarm that has been heat cycled, and the rest of it not. Or, since the factory normalizes the swingarm after production, now you have a part that has been welded and not normalized.

Long story short, by pure luck and a right fantastic gentleman on this forum, I got a basically brand new swing arm, and the gouged out POS is hanging on my wall. I feel better, my mechanic's insurance company feels better, and I can ride without thinking about when the "fix" will fail.
 

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Discussion Starter · #12 ·
I'm a paranoid guy as well and after my "mechanic" forgot to install the washer on my 900, well, needless to say I wasn't happy.

Aluminum is a tricky material, it has zero fatigue limit, meaning, it will inevitably fail at some point. I didn't feel comfortable with a repair job, since now you have a section of your swingarm that has been heat cycled, and the rest of it not. Or, since the factory normalizes the swingarm after production, now you have a part that has been welded and not normalized.

Long story short, by pure luck and a right fantastic gentleman on this forum, I got a basically brand new swing arm, and the gouged out POS is hanging on my wall. I feel better, my mechanic's insurance company feels better, and I can ride without thinking about when the "fix" will fail.
I remember your swingarm... so sad, Im glad you sorted it out.

I think I am just going to CAREFULLY smooth it out and bolt 'er on. Thanks!
 

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I bought a braced swingarm for my Monster which had worse chain 'bites' in it than that but nothing that would cause it to fail, however I filled the grooves with weld and ground it back to flat for cosmetic reasons.

Yours looks fine structurally but you could weld/grind if you're worried about it looking good.
 
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