This is what i did to convert my 2280 to a manual choke.
First of all i grinded off the ridges/steps on the fast idle cam,i did this a bit at a time to make sure i didn't take too much off.
I then rounded the end of the fast idle cam adjusting screw.
I then drilled a hole,slightly bigger than the groove in the fast idle cam.
I then used a small nut and bolt in this hole to stop the linkage moving.
You will have to grind the nut down a bit so it doesn't catch on anything,you can see this in the photo.
I had an arm and cable stop off an old carby which i slotted and bolted onto the choke pull off side of the choke shaft,i will braze this on when i get some fine rods.
Hope this might help someone out.