The best way is to vee it out thoroughly and weld it back on with a mig welder, but only do it in one second bursts and never let it get even remotely hot, leave it for a few minutes between the one second bursts. Another way if it is a stub is to machine up a new stub with a bit that fits in the port, open it up with a die grinder and mig it in that way. Or if it's a Matchless head, send me £20 plus the postage as I have a pretty good one spare!
Dave
thanks Dave, its a two port head,1940, 350 matchless, so need it fixed,not up to taking a chance myself, Pm me with your postal address and I will post off to you ,then tell me how much and the options when you see it, andrew .h.
I use STD wire but heat the cast iron with a propane torch first,I have done several repairs welding back on fins and with no cracking to the weld this way.. Dave..