I think I know the answer but wanted to check after seeing a note about someone being very good at welding alu.

I have a alu frame with a very small crack in the headtube, Can it be repaired/welded ?

How durable is debatable and it would be expensive. Try one of the specialist motorcycle frame manufacturers such as harris or spondon

Heat treatment is an issue depending on the exact alloy used

So not a No then, I dont mind spending as I really like the frame..

I don’t think they can be ‘properly’ repaired. Welding the aluminium causes a change in the hardness (due to the heat) which leads to an overly brittle weld.

Usually ali frames are welded and then heat treated afterwards to relieve the stress caused by welding and make the welds less brittle.

So unless you intend to get the frame re-heat treated the answer is no.

However, I had a cheap ali frame a few years back that had a cracked dowtube weld. I had someone weld the crack and plate it and it didn’t crack there again (went on a seat tube weld second time). So it can be done, but won’t ever be as strong.

There is a welded in Coventry who we use through work who seems to know his beans when it comes to welding. He does ali, stainless and ti welding and along with the commercial welding he does for us, he also does ti artwork so must know a thing or two about welding.

I can drop you his details if you want (note that i’m not sure if he’s ever welded a bike before).