Weird Weber 34 DAT behaviour in cold weather

[Pootle]

I've had a Weber 34 DAT conversion kit on my 1989 1.9 DG wasserboxer for a couple of years. I'm very happy with it, except for one thing. When the engine is stone cold, the engine runs fine. But after about three minutes, as the carb is warming up, it will not idle at all. A few minutes later and it's fine again. In spring and summer it never happens, it's only in January/February when it's less than 5 degrees or so.

The carb needs to stay on the fast idle cam for a couple of minutes longer as it is warming up.

The carburettor has alignment marks on the bi-metal coil housing. See here (from the Haynes manual for Weber carbs, thanks Diamond Hell):



See here for my carb:



If I loosen the three screws on the bi-metal coil housing and turn it, it should stay on the fast idle cam longer.

* Which way should I move it?

* Do I turn the whole housing?

* Has anyone else done this?

Other info: I have a Bluebird stainless exhaust which doesn't have the jacket providing pre-heated warm air to the carb. At the time I bought the exhaust the advice received from these forums was that the preheat jacket wasn't necesary (see here: https://club8090.co.uk/forum/viewtopic.p ... 954#p56613" onclick="window.open(this.href);return false;)

[Mocki]

you turn the whole body anticlockwise iirc, to tighten the spring.
are the water feedpipes the right way roound?
soundslike icing to me.