Roy,
Your picture is for 6 spring. I believe there are two different threads for the 6 spring, depending on year of bike, either 24 tpi or 28 tpi.
My picture attached is for 4 spring.
6 spring is MCA (Aston) Ltd, Pt no P117.
4 spring is MCA (Aston) Ltd, Pt no P110.
MCA (Aston) product is what virtually everyone sells.
The inner hub should just pull off the clutch centre (adaptor) - then you tackle the clutch centre with a puller.