Hi guys,
Thanks for the replies... and yup, you're right, it's for the throttle access &/or movement. What threw me is that on the 'big bore' 473(?) carb I got from Peter it has a real long choke arm that points in the complete opposite direction to the throttle so the hole in the mount could've been for that if you turn it thro 180

Peter says to junk the choke anyway

another 1/4oz lighter![sm=thumbup.gif]
Steve