I had 2 previous carburetted bikes. A Chinese made Lifan LF-125 bought brand new back in 2008 and a used 1993 Ninja 500 bought in 2009. Both bikes didn't need adjustment to the idle speed or the idle mixture screw. They all ran alright when warmed up. I got rid of them after riding each for a year. I now bought a used 2008 model carbureted PGO G-MAX 200 scooter. The engine is an air cooled single cylinder. This bike often need adjustment to the idle mixture screw. I bought this bike in winter. When I first rode it in temperatures of 10 Celsius, it has a slight hesitation when accelerating normally from a stop. The hesitation would be worse if I twist it real quick to 40%. When the weather got warmer, the hesitation went so bad that it's un-ridable when warmed up. It would idle OK, but when you twist the throttle, no matter how slow/fast you twist, the engine will die. That's when I decided to adjust the idle mixture screw, which when i turn counter-clockwise (leaner), the RPM went up, then I adjusted the idle speed down to factory spec 1700 rpm, then i adjusted the mixture screw again until the RPM is highest, then adjusted the idle speed, etc... At the end I turned counter clockwise 2 full turns. After that, the idle and the low RPM operation (from 1.7k to 4k rpm) was so much smoother and controllable. Through out the manufacturer OCI of 1000km, the engine will run leaner and leaner. For example, when i was 400km into the OCI. From idle, when I slowly twist the throttle a little, you can hear the engine bogging down / misfiring and wanting to stall. If I get the bike moving at 15mph (throttle 10%), and I slowly accelerate, the bike will bog down for 1 second, then takes off. If I twist the throttle quickly, the engine would respond immediately with no bogging down. Only slowly twisting will cause the bogging down. I solved it by turning mixture screw clockwise (richer). If i was 700km into the OCI, again, i have to turn clockwise (make it richer) of the mixture screw. When I finally changed the oil, I will need to reset the mixture screw (turn counter clockwise to make it leaner) for it to run properly. Engine temperature also seem to play a role too. When the bike is ran within town, low speeds, it seem to need richer idle mixture. But if bike was ran on highway 60mph (90% throttle 7k rpm) for at least 30 minutes, it seemed the leaner idle mixture is OK. I am a bit tired of taking the seat off to adjust the idle mixture. A bike requiring such frequent adjustment, Is this normal?