Thanks Mark and I would definitely take you up on your offer, who knows might even drive up to Brisbane but don't think the car would make it.
Appreciate your support but I've spent a few hours on this machine and feel I haven't got anywhere. Your photos are great and really make the forum a superb resource for many people.
If the decompressor is really to blame here I know someone who has a later Victa but I think there decompressor is sealed, wonder if they're interchangeable? Could try and put there's on mine.