How do you set the carb on a johnson mq-12a?

To set the carburetor on a Johnson MQ-12A, start by ensuring the engine is cool and properly secured. Adjust the idle speed screw to achieve a smooth idle, typically around 1,000-1,200 RPM. Then, fine-tune the air-fuel mixture screw by turning it clockwise until the engine stumbles, and then counterclockwise until it runs smoothly. Finally, make any necessary adjustments for optimal performance while observing the engine's response.