Thanks guys, I thought that would be the one, just confused myself looking at pictures in Roy Bacons Twin Restoration, theres acouple of pictures of swing arm models with the solid kind, including a SR and there were a couple with the folding type with internal spring but found thats more on the unit models.
The correct type was on plunger framed models, was confused so thought Id ask the experts.
Yeah big Oops Id swore that was a kick start when I found it lol