I really do appreciate all comments (any comments).

I ended up fitting a completely different tank and carb from another mower I have here, took me awhile as it was filthy, so had to clean it all up.

Anyway the result was it ran wonderfully with the other unit fitted.

So I have to have a closer look at the old one.

Thanks Joe & Grumpy.

Happy is he who penetrates the mystery of things.