Yamaha - Pilot Jet #42.5 Carburetor Fuel Metering Component 7CU-E4142-42-A0. Overview. Pilot jets are one of the first things I look at when an engine won't idle clean or feels off right off idle. It doesn't take much-just a little buildup or the wrong size-and the whole low-speed range suffers. I've brought plenty of engines back to life just by swapping in the correct jet. When it's right, the idle smooths out and throttle pickup feels crisp again.. Key Features. • Low-Speed Fuel Control - Regulates fuel flow at idle and low throttle for smooth operation.• Precision Jet Sizing - Calibrated at 42.5 for accurate fuel-air mixture in carbureted systems.• OEM Threaded Fit - Designed for proper installation and secure seating in the carburetor.• Improved Idle Stability - Helps eliminate stalling, hesitation, and uneven low-speed performance.. Engine & Boat Compatibility. Designed for Yamaha outboard engines equipped with carbureted fuel systems that utilize a pilot jet for low-speed fuel c