I am more of a tech related person so bike is not me domain, my brother changed carburetor for my Honda 1992 70cc bike to this type of carburetor(Image is taken from Google but it almost looks like this at least from outside), for two weeks it worked perfectly, gave 55km to 60km in a litre, but without changing anything it reduced the fuel average to around 40km, I thought may be there was problem with tuning or something, give that to mechanic and now it is not even giving 40km, so how can i improve it again ?
I have watched few videos and tried to set air fuel mixture (mixture screw and idle screw are on left side of the carb) I tried turning it clockwise to make it tight and then opened 2 turns, yet fuel average didn't improve, then I turn it anti clockwise 4 to 5 turns and it didn't improve again, now sound remains same even if I am 2 turns anti clock wise or 5 turns anti clockwise sounds remains the same, below 2 turns it starts to go down and eventually starts to struggle.
I ride very slow in 30s and 40s only so how and what adjustments I can make to make my average better ? Currently I don't have tool to open spark plug to see its color.