picked up an 1800 motor with a single carby set up. anyone tried this and / or have an opinion. the carby is a weber 40 dcnf 20 2c, made in Bologna Italy. haven't started it yet.

You talking Type 1 or Type 4?

Single Webers can be pigs to jet so hopefully PO has gone through the pain already

Light reading......
http://www.aircooled.net/vw-carburetor-options-selection-101/ 
If you can tune carbs then you'll be fine, don't be frightened!

My personal unqualified experience with DCNFs is that they spit a bit of fuel on bumpy corrugated stuff, but apart from that are nice enough to use.

type 4

A single carb needs preheat at the best of times

I have never seen preheat on a Type 4 and being a wider motor it is needed more.

Is it for your Type 3?

A bit of work needed in the cahnge over

the motor came with a kombi I picked up for parts. it was on a pallet and had been sitting in a shed for years. the owner bought it originally for his sons kombi but son rolled the kombi before the motor arrived. I was told it was a rebuilt 2 litre, but when I went to pick it up it was an 1800 with the single carb set up. not too worried as it was cheap. will try to get it started this week. Not going in the type 3 though, maybe in the goggomobil