28 series idle system

228 series idle system

The idle system supplies fuel to run the engine at curb idle and at off idle speeds up to the point where sufficient velocity is built up in the main venturi to operate the main jet system. The idle system consists of the idle discharge port, the idle jet, a passage or channel between the jet and the discharge port, an idle intake passage with a fixed air bleed, an idle fuel passage and an idle air adjusting needle.

NOTE: The idle discharge port on the 28 series is formed by a small brass plug pressed into the throttle body in line with the closed throttle plate. Int he 228 series, two calibrated idle discharge holes are located in the body with one hole just above and the other hole just below the throttle plate when in the closed position. The idle needle valve is located in the throttle body at the lower idle discharge hole to control the dischare of the idle fuel-air mixture.

IMPORTANT: To lean the idle fuel mixture on the 28 series, you turn the idle mixture screw OUT (counter-clockwise), to lean the mixture on the 228 series you turn the idle mixture screw IN (clockwise). The idle mixture screw functions backwards from traditional carb setups on the 28 due to the design and idle mixture screw placement.