It is amazing how these posts come up when you need it the most, Sammy.
I have been trying for a year to get my idle down below 1300, but to no avail. I read this post, looked on a couple spare ZS's I have in the garage, and located this deceleration bypass valve. The ones on the spares had a small clip on them, to hold them in position I presume, so I looked at mine on the 7, and the rear was fine, but on the front carb, the adjustment screw was broken off, and I could feel some air being sucked in. Well, off came one from the spares and I replaced the broken one. The small gasket was also well worn.
Well, I now have a steady idle of 800. What a differance it made.
Thanks to this post, and your super description, one more step made in the learning curve.
This is what makes this forum the best./ubbthreads/images/graemlins/thumbsup.gif
Paul