MIKUNI 004.078 Hex Main Jet 90

Large hex type used in most Mikuni carburetors. Mikuni # 4/042.

The MIKUNI 004.078 Hex Main Jet 90 is a replacement carburetor component designed for applications that use a compatible Mikuni hex-style main jet. As a fuel-metering component, the main jet helps regulate fuel delivery through the carburetor’s primary circuit during higher-throttle operation. This makes it an important service part for maintaining consistent engine performance and supporting proper carburetor calibration.
Use the MIKUNI 004.078 Hex Main Jet 90 when servicing, rebuilding, or tuning a compatible carburetor. The size 90 designation identifies the jet’s calibrated fuel-flow specification, allowing technicians to select a replacement that matches the requirements of the engine and carburetor setup. Always verify carburetor compatibility, jet style, and application requirements before installation, since main jet specifications can vary between models and operating conditions.
This replacement jet is supplied as one individual unit and is suitable for repair shops, powersports technicians, and experienced do-it-yourself mechanics. For best results, install the jet with clean, properly fitting tools and avoid forcing or damaging the precision-machined threads and metering passage. After installation, inspect the carburetor for cleanliness, confirm that all components are correctly seated, and adjust the overall fuel system as needed according to the equipment manufacturer’s service procedures.
Brand: MIKUNI. Part Number: 004.078. Product Type: Hex main jet. Jet Size: 90. Unit of Measure: Each. Select this genuine MIKUNI replacement component to help restore the intended fuel-metering configuration of a compatible carburetor and support reliable service during maintenance or tuning.

Features:

• Brand: MIKUNI

• Part Number: 004.078

• Product Type: Hex main jet

• Jet Size: 90

• Application: Replacement, maintenance, and carburetor tuning for compatible Mikuni systems

• Unit of Measure: Each