I went back and had another look and found half the problem.

the top butterfly control arm had been bent down so would never close the throttle so i've straightened this and i now don't have it trying to destroy itself with revs.

the one thing i think i'm missing is a spring to return the butterfly to closed, i've used some rubber bands for the time being but they are a bit too strong for the opposing spring. can anyone confirm/show me a picture of their assembly???

picture below shows the rubber band assembly currently used

http://i492.photobucket.com/albums/r...413_172715.jpg