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Cracked Swing Arm At Linkage Pivot!


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  • 8 years later...

Hi, I have a similar issue, 2000, Montesa Cota 315R, I have found a crack at one side of the swinging arm pivot point (where the long bolt goes through). The crack runs the length of the bush (aluminium surrounding the bearing). Can this be Veed out and welded? Or? :-(

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You should find plenty of welders in the midlands - search alloy welding, aluminium frame repairs, and similar phrases.


The reason it has cracked is probably because of bearing corrosion or corrosion between the outer bearing housing and the aluminium.


Before it is welded it needs the bearing removing and a solid steel form, with the same OD as the bearing pressing in. If it is welded without support it will shrink and IF you can get the new bearing in it will wear rapidly.

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It has been welded, V cut and welded nearly all the way down, but not to the bottom, one end slightly damaged and built up, so I need to file down. I can feel the original fracture line lip inside, so may try to smooth that lip with a file. Internal diameter seems comparable to other side of arm (as measured with vernier). Will report back.




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So assembled, and bearing is uncomfortably tight when inserting bush, bore is slightly out of true after weld repair. Question is how to get it back in true. Machine (how, milling?), file, sand with drill rotary sand attachment?

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You could do it with a small hone and drill, the type they use on car wheel cylinders :thumbup: 


Aluminium isn’t the best material to hone but it should do it


The only problem you may have is the crack on the inside may act as a stress riser, and it will probably crack the weld (just keep an eye on it)

Edited by suzuki250
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