Tickover adjustment Weber conversion

How do adjust my tickover down from about 1150 to 800-850? there is a gap of about 3mm between the adjustment screw and the base plate it adjusts off. Also, should the yellow spring just shown disappearing bottom centre be fully compressed, it appears to do nothing in this state. Cheers, (it's taken me nearly an hour to get the pic to upload, I'm a technomuppet…)
 

Not sure which screw you mean but this should help, the screw in the for ground with a small gap is ok, it adjusts the choke idle speed.

Have a look here for where the idle screw is, I run my carb car at 950rpm as found 850 to low and things start to rattle at that speed and if you turn on lights, blower, heated window it drops even further.

https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=big-block-carb-engines_2%2Fidle-adjustment-1-8

Thank you, that's the badger, I didn't touch anything as I knew I was on painkillers and I'd just screw things up, pardon the pun. This was exploratory prior to setting the car up properly. The book I have shows 1000 for non electronic ignition, 850 for electronic, I have the halfassed Hall effect system, (I think).

The book may refer to a Pierburg carb as Webber's are not standard issue from Vw.
I would just try it out, count or mark where the idle screw is now so you can adjust it back if it goes pair shaped.

Get the car nice and warm before adjusting any thing and after moving the idle screw give the car a good couple of blips on the throttle so it settles.

Many thanks mark1gls, It will be for a Pierburg, but I have an automatic and I don't want tick over too high. I don't intend to touch the mixture screw, just the idle adjustment. It's embarrassing with it revving it's jacks off (to my ears) at junctions, but I also don't want it shaking like a 3cyl. Perkins!