Zama Main Mixture Adjustment Screw Carburetor

Zama main mixture adjustment screws, also called high-speed needles, H screws or main jet adjusters, are replacement parts for Zama carburetors. They meter fuel at high speed and under load. Zama carburetors are common on chainsaws, trimmers, blowers and other small engines. A worn or damaged screw can make the engine run too rich or too lean.

Key Features:

• Controls the fuel mixture in the main (high-speed) circuit, which sets fuel delivery at full throttle
• Precision-tapered needle tip seats in the carburetor body for fine, repeatable fuel adjustment
• Replaces worn, bent or damaged screws that cause hard adjustment or an unstable mixture
• Made for Zama carburetor bodies. Different carburetor models use different screw part numbers.

Installation Notes:

• Remove the main mixture screw before removing or reinstalling the carburetor nozzle assembly.
• Inspect the needle tip for deformation. A damaged needle or seat makes the needle very sensitive and hard to adjust.
• Seat the screw lightly, then back it out to the engine manufacturer's recommended starting setting. Fine-tune with the engine warm.

A correctly adjusted main mixture screw helps restore smooth acceleration, consistent power and reliable engine operation. Select the child item that matches your carburetor model.