I a have a Zennco yb 125 motor cycle on a 58 plate this is a Chinese copy of a Honda cg125 engine its running rich to the extent i don't have to use the choke even from COLD.
the carb is carrying the TK mark in the casting along with the number Z22PA-SLC4C13
the tick over screw is on the right side of carb, what looks like the small mixture AIR screw is on the left side in front of the choke linkage
any idea's on the needle jet position and air screw setting

chris, November 2010

How do you know its running rich? is the plug sooted up? anyhow,you've found the small air/mixture screw BUT it depends if its towards the engine side of the carb body or the air filter side as to which way you turn it.Turn it clockwise to weaken the mixture if its the engine side and anti-clockwise to weaken the mixture if its on the air filter side but only approx 1/8th turn at a time, generally 1 1/2 tuns out from seating is a good place to start. Could also be your float level is too high or you have a punctured float both causing flooding/rich mixture.

Chris P.Duck, November 2010