User Manual
3
Low-Speed Needle
Rich
Lean
.21 and larger 2- and 3-needle slide valve carburetor
Decrease
Increase
Mid-Range Needle
Low-Speed
Needle
Idle Adjustment
Rich
Lean
.21 and larger 3-needle slide valve carburetor
High-Speed Needle
Fuel Inlet
Idle Adjustment
Rich
Lean
Decrease
Increase
.12, .15 and .18 2-needle rotary carburetor
Low-Speed Needle
Idle Adjustment
Rich
Lean
.12, .15 and .18 2-needle rotary carburetor
High-Speed Needle
Fuel Inlet
Idle Adjustment
Rich
Lean
.12, .15 and .18 2-needle slide valve carburetor
Low-Speed Needle
Rich
Lean
.12, .15 and .18 2-needle slide valve carburetor
Engines .21 or larger may also be equipped with a
slide valve carburetor that includes three inserts of
various diameters. These are sometimes referred to as
“restrictors” or “venturies”. These carburetor inserts are
used to alter the power curve of the engine along with fuel
economy. The three diameters have the following effects.