Carb Problems

[bombhead]

I have an RF 400 with a Mikuni BST32 carb. The bike was working quite happily up until 1 month ago. I haven't ridden it since then but now that I've came to start it it, it won't start. I know the tank is slightly rusty so I've taken the carbs off and cleaned them. The 1st carb (far left) is now leaking petrol and the bike is backfiring. What could be the problem and what is the air/fuel screw setting ? I've been told it's 2/12 full turns out but this is having no joy.
I'm pulling my hair out..........help !!!!!!!

Regards
Darren
 

[Red01]

Fix the leak first and then see if that cures the backfiring, since a lean condition causes that.