The following should be observed before attempting any adjustments.
- Thoroughly warm the engine. If the engine is cold, be sure that it reaches operating temperature.
- Check the torque of all carburetor mounting nuts and assembly screws. Also check the intake manifold-to-cylinder head bolts. If air is leaking at any of these points, any attempts at adjustment will inevitably lead to frustration.
- Check the manifold heat control valve (if used) to be sure that it is free.
- Check and adjust the choke as necessary.
- Adjust the idle speed and mixture. If the mixture screws are capped, don't adjust them unless all other causes of rough idle have been eliminated. If any adjustments are performed that might possible change the idle speed or mixture, adjust the idle and mixture again when you are finished.
Before you make any carburetor adjustments make sure that the engine is in tune. Many problems which are thought to be carburetor related can be traced to an engine which is simply out-of-tune. Any trouble in these areas will have symptoms like those of carburetor problems.