Carb leaking at the throttle butterfy
 

Hi all,
I have an interesting leak on the carb on the side where the large spring for the throttle is. I noticed in the last months that the scoot is reving up a little bit on idle, but other than the fact that it is anoying, it is not affecting performance at all. Anyway, I checked the manifold and all the hoses and everything is good, and than I noticed the gunk that forms as a gas residue on the spring and around its base. My question is, is the spring with the butterfly inside removable and how to do it, because I only see a shiny steel fitting closing the hole from the other side? Is there a gasket or a seal or only a bushing inside and is it replaceable or I need a new carb? Thanks all.
Zlatko