Over time, improper adjustment, contamination, wear, physical damage, or repeated over-tightening may require the Fuel Assist Screw assembly to be rebuilt or certain components to be replaced.
When assembling the Fuel Assist Screw, carefully inspect the needle tip, spring, O-ring, washer, and screw body. Any damage, contamination, deformation, or incorrect assembly may cause unstable idle, improper fuel delivery, difficult starting, hanging idle, or poor low-throttle performance.
IMPORTANT: Never use a flathead screwdriver or any tool to adjust the Fuel Assist Screw.
The torque produced by screwdrivers is far too high, especially when turning the screw clockwise toward the end position. This can easily break the needle tip inside the carburetor body.
The XTNG Fuel Assist Screw uses a defined “Zero Position” as the official adjustment reference.
The Zero Position is reached when the inner side of the knurled adjustment knob just lightly contacts the carburetor surface. At this point, the fuel passage is considered fully closed.
This is the true tuning starting point.
Although the screw may still physically rotate further clockwise, those additional turns have no tuning meaning and must not be included in adjustment calculations.
From the Zero Position, rotate the screw counterclockwise for tuning. Typical baseline settings are generally between 1.0 and 1.5 turns out depending on engine setup and riding conditions.
Always make small adjustments while monitoring idle stability, throttle response, starting behavior, and low-end performance.
The above content will be included in the next version of our user manual.
