Bit of tinkering to address the throttle only getting 3/4 ish. I moved the cable further up the throttle arm to try it. It didn't work though as the longer arc needs more cable travel.
The arm has a big hole so needed a flanged bush... luckily I had a suitable bolt.
OK. I've sorted it. I traced the issue to the original throttle linkage flexing. It runs from the throttle pedal to the nearside chassis rail and is only supported at the ends where the arms are. The new arm sits next to the offside chassis rail, the rod bends slightly preventing full throttle.
I have cut the rod in half as I don't need it to go to the nearside, the loose rod will be supported on a bracket with a bronze bush in it. It doesn't need a retaining pin as there is a split pin at the other end.
I've had a few carb issues. Mainly sticking needle valves (yes it has 2..) and heat transfer from the heads but that is all sorted now. I've been out and about a fair bit recently. Tested the acceleration on the old industrial estate near here... it's loud, obnoxious and stupid fast but is easy to Potter around in too.
It also left a wriggly number 11 when pushed too hard..
Long story short. Plans have changed this weekend so I've booked in for a day at the drag strip near York. Gonna have a play out.