Cracked Head Tube (Al MTB)

[bobb]

A mate of mine has bought a second hand Scott MTB. A reasonably good one (about a grand new a couple of years ago) but he has a problem which he didn't notice when purchasing. (Please don't ask about warranty, getting his money back etc. as it's not relevant to what I'm asking and is being pursued)  

There is a small crack in the head tube. It can just be seen in the rather shitty photo I took below:



He has a mate who says he can weld it up. Now I'm not questioning the guy's skill and experience, but I'm pretty certain he doesn't usually do bicycles (usually cars, motorbikes and other stuff). Is there anything to look out for and will it be ok once it's welded up?

Ta.

[LittleWheelsandBig]

I assume it is 7005 and doesn't need special post-weld heat treatment.  Machine the head tube carefully after the welding, it'll definitely distort and headset tolerances are very tight.

If he is a good TIG welder and has played with similar Al before, he'll know the sort of prep and TIG rod required to do a decent job.  He needs to chase the crack all the way to solid metal, leaving a crack initiator isn't good on a head tube.

[bobb]

Ta - yes, I should have mentioned it's 7005....