Some questions:

the emulsion tubes on small bore 250's are very tiny!!! As a result they also wear a lot faster (apparently a lot of teh japanese sports 250's need replacements about every 20-30 000 depending on how hard it was ridden; but given that is a sports 250 it has probably been pushed).

That was the issue with my old fzr250 and was making it run rich. Instead of fixing I sold it and bought a new bike.

 

I took my carbies down to the mechanic when I went to get new float bowl gaskets and he confirmed that the screws below the drain screws are for setting the mixture. Raaqi you listening? You will want to unwind them to make your mixture richer but what you do to one you must do to the others. Hope this helps you with your lack of front wheel airtime, lol.
I also hijacked the parts departments’ computer and managed to print off an assembly drawing of the 250's carbs, now I can burn the one for the 400.

Can I email it to someone so they can host it on the site somewhere?

 

The revving and spluttering sounds like a mixture problem. I would look into getting the gear box checked if a clean and reset of the carbs doesn’t work. Sorry to hear your bike isn’t well, I know the feeling too well. I have only now just got on top of all the problems since I bought it 5 months ago. It doesn’t help on an apprentice wages either. I found the best thing to do it learn how to do it yourself, it will save you big money and maybe even get you out of a tight spot one day.