Are the idle speed knobs red now? Maybe red in other markets?
I just looked up the fiche for the 2012's and all I see are the normal choke and idle speed knobs.
I think Point37 called it.
The passage is not machined on U.S. models, but on yours it would lean the mixture for hot starts.
Could it be an altitude adjustment to lean the mixture when you go up . Honda had a set up like that on their atc90/110 and ct90/110 in the 70s or 80s (in what country are you located).
Robert