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Swingarm reapir

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Giddy folks - wonder what we all think about reapiring a swingarm the has had far too long on flogged bearingsm causing an ovalised / beaten inner surface where the bearings sit?

Local alloy expert said I can't get the tip of the welder in deep enough to lay a good layer of alloy down before machining, so next option is to hone out a minimal amount and press in a 1mm sleeve - ..... anyone else have a better solution?

John

PS I mean repair :smirk:

Edited by kiwijohn

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Ultimately, the best thing would be to cut away the existing pivots using a mill to finish the cut, and replace them with freshly machined pieces.

Alternatively, boring and sleeving could be workable if the original pivot is not made too thin. In doing so, the original pivots should be narrowed on each end so that the sleeve, which should be a press fit, can be welded to both ends of the original, and the weld then finished to the correct width.

Sounds like a lot of work, though, eh?

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Maybe do a little research to see if there are any shops in your area that can do plasma spray buildup on aluminum. This used to be a very common repair in the aircraft industry to fix bearing surfaces and the like. In the swingarm, the bearing race should put the machined plasma (multi-alloy metal spray) into compression where it works best. The machinist will need to know where to put the center of the pivot bore but if there are 3 points he can touch off on where it isn't egged out, he should be able to resotre the bore properly. Good luck.

Put this in the google search bar and lots of places show up:

"plasma spray metal repair new zealand"

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answers like these are why i frequent this forum and appreciate this thread. TT has to be the best place on the net to get intuitive answers from experienced people for tough motorcycle related problems.

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Thanks gentlemen :smirk:

the cost of a new swingarm here in nz is in the thousands, so repair is a good option. Also can't find any used options so I guess i'm stuck.

The sleeve is probably the best (read cheapest / easiest) option, but i love the plasma idea !

we are also toying with the idea of fitting a temporary axle after filling the axle with coldweld, then removing the temporary axle to leave a solid smooth surfaqce... but I don't believe a liquid weld can handle the torsional loads from a swingarm flexing sideways?

Will keep you all up to date :smirk:

Thanks again

John

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Machine it out and press in a sleeve. No need to weld it. We do it all the time on components at work that have a tougher life than a swingarm. Use good alloy steel and you shouldn't lose any strenght, probably gain some. Should go forever with the right lubrication.

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For the vast majority of my bikes, it would be easiest to just buy a used replacement off ebay. But if its an oddball bike where that isn't an option, I would be inclined to mill out and press in a sleeve.

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Cool - my engineer buddy has a guy who does the plasma spray so will have a quick look at that, but I think sleeve is the go !

Thanks fellas.

John

Still... a 2nd hand one would be so much easier ha ha if I can find one!

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Ultimately, the best thing would be to cut away the existing pivots using a mill to finish the cut, and replace them with freshly machined pieces.

Alternatively, boring and sleeving could be workable if the original pivot is not made too thin. In doing so, the original pivots should be narrowed on each end so that the sleeve, which should be a press fit, can be welded to both ends of the original, and the weld then finished to the correct width.

Sounds like a lot of work, though, eh?

^ I agree. But, I really doubt there is enough material to bore & sleeve it and have it survive very long.

If you can't get a new/used part, then replacing the worn section is probably the best bet. Additionally, the swingarm may need heat treating after such extensive welding.

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I can't imagine that there is so little material around the pivot that you can't open the diameter up 2 mm (0.079") to press in a thin wall sleeve. Take some measurements and see what you have for wall thickness currently.

If you have something like 13 mm wall thickness and take it down to 12mm, I can't forsee that being a big issue. Now, if it's only 5 mm thick around the bearings and you take it to 4 mm, that could give me some room to worry.

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^ I agree. But, I really doubt there is enough material to bore & sleeve it and have it survive very long.
Exactly why I qualified the suggestion that way. The "catch 22" in that is that leaving more material in the original pivot eye makes the sleeve more difficult to make and fit. Sleeving is a clear "second choice", IMO.

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You may want to look into boring to clean up the holes, look for the next smaller OD bearing and have a sleeve made to fit the cleaned swingarm bore and the new smaller OD bearing.

You will have to take good care of your new bearings...if they stick and the sleeve spins you're gonna be in trouble.

I would try and leave as much swing arm material as possible.

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