[saki302]

If you look where the secondary throttle shaft is, there may be a set screw (flat head) which can adjust the opening. On mine it is accessed from underneath, now that I know where it is, I can get to it with a flat head bit and a low profile screwdriver ratchet. There isn't much room under there to work.

Some people replace the whole thing with an allen set screw to make adjustments easier.