Decided to try this yesterday as I was giving the bike and service anyway.
Ended up using the welder for the sides and bottom but couldn't get to the top of the exhaust as obviously the engine/bike was in the way, so used the JB Weld on that bit.
No leaks, all seems fine for now.
A bit nerve racking using the welder for the first time.. but I think I done OK, although it'll never win any beauty prizes.. but it'll be covered in road grime by the end of the week and won't be seen!
I think I'm been rather unkind to my little Donkey, as I ride it all year in all weather and clean it once a year and stick some ACF50 on it.
The exhaust does not look like it's going to come off without a huge fight at the headers, and I really don't have the time/desire to get into that right now..
One my Pan Euro refurb is complete I may do one on the Donkey too.. it's been very good and has never let me down despite the miles and abuse I throw at it...