i had a 125 sherco 2005 and the mixture screw went the opposite way!! screw in for making it weaker and out for richer. dont know if yours is the same carb
if the bike is not running clear reset the mixture screw by screwing all the way in and then take it out 1 and a half to 2 turns ( depending on wear the bike runs best ) Then set tick over up ,as changing the mixture also affects tick over slightly.
also make sure the bike is hot when setting it up.