@mf448kxn6 thanks, the acorn nut might as well be made from cheese! – I was able to extract the thread – just need a replacement.
I’m confused over the main jets though – the GT250 parts catalogue states 95/97.5 (front/rear) with the stock exhaust.
My GT250 has a stock exhaust (and is staying stock) – the jets are 92.5/95 – based on your comments, I should stick with these?