My two bob's worth.
I think that they have inserted the guide at the wrong angle and have cut the seats to suit.
Probably need a GOOD machinist to set up the head and bore the guide hole correctly and make an oversize guide to fit. Would most likely need a new seat as well.
I think that you need to have a serious conversation with the mob who did this bit of butchery.
Trev.
Very much my own feelings, but it is a complicated situation with the 'mob' who have done this, Service Exchange Parts, Kegworth.
They did the original work for the person I bought the bike from, a very decent person. He got in touch with them when I discovered the problem and arranged for me to sent the head back for repair only to have it returned in the current situation.
Further investigation shows that they look to have machined and fitted a sleeve and welded it in, see attached, which has been left in a bad state. They have not cleaned the face up, which is left with a raised rim of weld such that the bottom valve spring washer does not sit on the face but tilted on the rib. They have also fitted a used guide which is different from all others they have fitted of unknown size, std, oversize?
The seats are supposed to have already be change, original work, thought I'm not convinced it/they have been?
All in I am not at all impressed and very reluctant to send it back to them, but since I did not originally engage them I am not in a position to make any direct demands on them only the guy I bought it from.