How to tune Maruti Zen Carburetor?

OK, if you are going to tune up an engine, first you need to understand there are two systems involved, one is the ignition and the other is the fuel system. Assuming your valve timing is OK and all your cylinders have the same pressure, then you have to time the ingition of the engine, you can check the timing specs in the shop manual, it's usually around 8ยบ BTDC (that is, the spark occurs eight degrees of crankshaft roataion before the pisto reached top dead center, or the uppermost part of its movement). Once you have done that, you have to adjust your idle screw, this regulates the amount of air entering the carburettor when idling, the more you open the screw, the higher the idle will be, if you tighten it too much, then the engine will become "rough" and stall. This screw is usually opened 3.5 turns counterclockwise from fully tight. Regading the caburattor, they have a lot of parts, but there are only three adjustable ones, 1) The idel screw, 2) the acceleration injector pump lever, (this "squirts gasoline into the carb when you press the pedal), have a friend stomp the accelerator pedal while you look down the throat of the carb, if you see a gasoline squirt, you are OK. 3) the float level, you adjust this by bending the float support up or down, keep the level to spec ot 2/3ds from the top edge of the float bowl. (for this you have to remove the top cover of the carburettor, so if the car is running I would do all the others first, since this is quite touchy. The carburettor float bowl works in the same way as the WC in your bathroom, open the water tank of the WC to see a larger version and see how the thing works (the engine will use up gasoline just like when you flush the toilet and the float will prevent the bowl from overflowing. Try to use original specs, the ones I gave you are general and will get your car running but it will not pass an emissions test. Good luck.