T3 carb question

Got a T3 with Dellorto VHBT 30 C carbs, does screwing the mixture screw in (clockwise) richen or lean the mixture? Or is it all a bit more complicated than that.

If you mean the small idle screw: screwing it in reduces the amount of fuel going through the by-pass passage.
Make sure you have checked that the float heights are accurately set before starting any setting up. Just open both idle screws by 2.5 turns from the closed position to begin with. Fine tuning at the end of the whole setting up process can be carried out, beware of setting them too closed as it will weaken the idle mixture and the engine will hunt.
The bigger knurled screws act as closure stops for the throttle slides. They should only be moved when you have the throttles opened by the twist grip or you run the risk of the sharp points on the ends of the screws digging in to the slides. Screwing them in increases the flow beneath the throttle slide and so increases engine speed.
You really need vacuum gauges or one of the differential pressure devices on eBay to set them up properly.

I set mine up by ear, I have some old mercury column gauges but don’t bother with them any more.
Set both mixture screws to about 2 turns out and start it up, give it a little run to get it warm and clear of choke, then just play with each of the mixture screws, winding them in and out till you get the best / fastest tickover. Try doing it with the other plug cap removed, that’s easier.
Repeat for the other side.
Make sure your choke cables are working freely, try oiling them as they probably haven’t seen any in their life. Make sure the choke slides are sliding freely, the rubbers at the bottom are in good condition and they drop down fully so you have free play in the cables.
Give the carbs a good clean out before doing this, including the accelerator pump assembly up inside the main jet body. Parts 63,4 & 5 in the diagram here
For balancing, I do it by ear, just listen to the clicks as the slides drop, if they are about at the same time, then that is good enough. It is likely it will change as soon as you move the bars anyway.

One more point, once you have it set up to your liking, you may find it difficult to start when hot. If that’s the case try turning both the mixture screws quarter to half a turn further out.

Thanks all. Any one seen my little screwdriver? its in the garage somewhere