Need help adjusting carb
#2
Senior Member
The 3221 and 3222 are butterfly type carbs. They have a butterfly stop screw near the lever, and on the other side of the carb the large main needle and an excenter type idle setting plate.
First set the butterfly so it will admit mixture to the engine. A modelling pin should be able to just pass.
Then the main needle should be set at about 3 turns open. A primed engine should now be able to start at wide open throttle. Adjust the main needle leaner, until the engine falls into a nice even firing with just a very occasional fourstroking miss.
Now slowly reduce throttle. If the engine goes rich, the excenter plate should be moved clockwise, and vice versa.
To do this, first loosen the set screw (nearest to engine) Now the excenter screw can be used to adjust the mixture. Clockwise is leaner, anticlockwise is richer.
When done, idle transition should be crisp. If the engine hesitates, slighe richer idle is needed. If the engine stutters, a leaner idle is needed.
Gently fasten the set screw, and you are done.
First set the butterfly so it will admit mixture to the engine. A modelling pin should be able to just pass.
Then the main needle should be set at about 3 turns open. A primed engine should now be able to start at wide open throttle. Adjust the main needle leaner, until the engine falls into a nice even firing with just a very occasional fourstroking miss.
Now slowly reduce throttle. If the engine goes rich, the excenter plate should be moved clockwise, and vice versa.
To do this, first loosen the set screw (nearest to engine) Now the excenter screw can be used to adjust the mixture. Clockwise is leaner, anticlockwise is richer.
When done, idle transition should be crisp. If the engine hesitates, slighe richer idle is needed. If the engine stutters, a leaner idle is needed.
Gently fasten the set screw, and you are done.
The following users liked this post:
Fly Low71 (09-23-2025)




