So... i have a nc21 its a KM model, dont think that matters much. Anyway i took washers out of the inlets which were at somepoint installed to restrict the bike. they sat in the carb mounting rubbers that join the carbs the the engine. From what i jave read thats a pretty standard way to restrict the bike.
Now that the bike is back together it will only just idle if the choke is on full and if you touch the throttle the engine stalls.
I assume i just have to adjust part of the carbs but i have no idea what i would need to adjust or what it would look like.

Any help would be very much appreciated.

I have no experience with a restricted NC21 setup but, assuming you did not inadvertently create a problem with the carbies while removing the washers, you may find that the jetting is not standard. This would be possibly part of the restriction process, otherwise the fuel flow would not suit the restricted air flow. Can only suggest that you inspect the carbies for the correct jet sizes.

The VFR400K is an old motorcycle training school bike.

The carb restriction sounds like a UK thing? It doesn't give your location in the profile.

Possible the carb rubbers are not fitted properly causing an air-leak.

Did you remove the float bowls and check the carb jetting as magg has already suggested? It's not always done but restricting the inlets properly often requires the bike to have smaller mainjets.

It should still idle and run ok though so I think something wasn't re-assembled correctly.

Thanks guys ended up me being a moron, i simply diddnt have enough fuel in the tank, switched onto reserve and bike ran fine...... what a ******

And its nice to fine someone who knows what it is :)