On older engines which use a carburetor, the choke is a common repair issue. The choke is the assembly which controls air flow into the carburetor and thus the amount of air in the fuel:air mixture being burned by the engine.
Common Choke Problems
The most common problem a choke will have is “sticking” - either staying open or closed during startup or operation. This is usually caused by carbon buildup or foreign matter obstructing the operation of the coke. There are several remedies for this, usually involving injecting choke cleaner or physically cleaning the top of the carburetor where the choke is located.
Worn return springs
Another common problem is similar, but involves the choke not returning to its default position (usually closed) after the throttle has been pumped. This sticking is often due to the return springs being worn or broken.
Proper Care and Maintenance Of Your Choke and Carb
Like anything on your engine, your choke and carburetor as a whole require routine maintenance to stay in good order. Most engine manufacturers recommend the use of carburetor cleaners or fuel additives to help burn away and keep carbon buildup from becoming a problem and avoiding choke repair. On many, occasional carburetor tear-down and rebuilding is also recommended.
The choke is vital to the carb's proper operation in controlling air flow. It can also, secondarily, be responsible for fuel intake into the carb as well, depending on design. Keeping yours properly maintained is important in avoiding choke problems.