Where does that spring go?? Honda 3.5hp OHV GX110?

Honda 3.5hp OHV GX110 engine fitted to a Templar Tiller Rotovator. Had to take the head off, as one of the valves was stuck open. Put it all back together, and a spring has fallen off and I can't work out how to put it back.. I am sure it is part of the throttle linkage, as the lever is now not attached to anything, but can't see where to put it back. Black spring 100mm long with the spring bit towards one end.
Any help appreciated - Thanks!