This is the method for DIY to adjust their air fuel ratio of 4G15 carb.

1) Warm up engine first(run 5-10 mins)
2)Shut off engine
3) Back out on the idle speed screw until it justt doesn't touch the throttle linkage. Then screw it in back about 11 turns
4) Screw in the A/F mixture screw until it stops(do not force tighten)
5) Screw out the A/F mixture screw 2 full turns
6) Start the damn car. It will run like its choking. As long as it's running it's ok.
7)
Now turn in the A/F screw until engine dies. If this happens, turn out
the A.F screw half turn at a time to bring it back. (try to start the
car of coz)
8)Continue to turn out the A/F screw at half turns every
3 seconds. Engine will pick up speed. Continue to screw out until the
point engine runs worse. When that happens screw back in half turn
every 3 secs to the point engine runs smoothest.(do this by ear or
watch engine vibration)
9) Now set the idle speed. Go on the air
conditioner. Watch the tachometer. Turn in the idle speed screw until
rpm is around 900 to 1000 rpm.
10) Now it's ready to rumble..

good info, for user Wira or Saga with 4g15 engine. But is this work for other 4g series engine? Hmm?