IDLE JET 40-45-50-55-60-65-70-75-80-85-90-95 F8 for WEBER DCOE #74821$ 6.1 ‹ › ‹ › ‹ › ‹ › ‹ › Part number: 74821Made in: EUCompatible with:Family: DCOE40 DCOE 20-21 - pn: 41165.059 (2 pcs)40 DCOE 34-35 - pn: 41165.054 (2 pcs)40 DCOE 44-45 - pn: 41165.065 (2 pcs)45 DCOE 38-39 - pn: 41165.060 (2 pcs)Family: IDA46 IDA 2-3 - pn: 41165.060 (2 pcs)48 IDA 1 - pn: 41165.060 (2 pcs)Idle Jet Type F8 for Weber DCOE - MPN 74821 F8 calibration: This idle jet is designed for the idle and progression circuits used in Weber DCOE carburetors. The numerical size, such as 45, 50 or 55, determines the fuel-metering orifice, while the F8 designation determines the air-bleed calibration and therefore the relative richness characteristic of the idle and progression circuit. Both values are important. Two idle jets with the same numerical fuel size but a different F-number can produce a different mixture characteristic because the amount of air mixed with the fuel is different. These jets are manufactured in the EU and have been developed with particular attention to fit, repeatability and compatibility with original and aftermarket Weber-style carburetor components. The external profile has been specially adapted to provide reliable seating and fit within the idle jet holder. This geometry is intended to provide broad compatibility across original Weber components, later production parts and aftermarket replacements, where small differences in holder geometry can otherwise affect installation. For improved consistency, the jets are machined and calibrated on the same production machine rather than being mixed from multiple machines or unrelated production batches. This helps maintain highly consistent dimensions and calibration from one jet to another — particularly important when matching jets across multiple carburetor barrels. Each jet features a clearly visible black size marking for easier identification during installation, carburetor tuning and future servicing. Available sizes are 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95. Select or specify the exact size required for your engine and carburetor setup. The illustrated jet is marked 45 F8. Other supplied sizes will carry the corresponding size identification. This replacement part is suitable for carburetor tuning, servicing and restoration work where accurate calibration, repeatability and dependable fit within the idle jet holder are important. Reference/MPN: 74821. What Is Included One F8 idle jet, MPN 74821, in the selected sizeSpecially adapted external profile for reliable fit within the idle jet holderBlack size marking for clear and easy identificationMade in EU. Tuning Tips The idle jet affects considerably more than idle speed alone. In Weber DCOE carburetors, the idle circuit also supplies fuel through the progression phase at small and moderate throttle openings before the main circuit becomes dominant. Incorrect idle jet calibration can therefore appear as hesitation, surging, poor low-speed response or an excessively rich mixture during normal part-throttle driving. The numerical jet size controls the fuel quantity, while the F8 designation determines the air-bleed characteristic and therefore influences the richness of the idle and progression circuit. Both must be considered together when tuning. As a general principle, increasing the numerical jet size increases fuel delivery and tends to enrich the idle and progression range, while decreasing the size reduces fuel delivery and tends to lean this part of the calibration. Make changes in small steps and change only one calibration component at a time. Evaluate throttle response and mixture behaviour under repeatable operating conditions rather than judging the jet only from stationary idle. Before changing jet size, verify that the carburetor is mechanically correct and properly synchronized. Float level, fuel pressure, ignition timing, throttle synchronization, mixture-screw adjustment and progression-hole exposure should be checked first, as problems in these areas can easily be mistaken for incorrect jetting. For multi-carburetor installations, use matching idle jet specifications and sizes in corresponding barrels unless the engine has been intentionally calibrated otherwise. A wideband lambda/AFR meter is strongly recommended when making final mixture adjustments. Important Fitment Note This F8 idle jet is intended for the following Weber DCOE applications: 38 DCOE40 DCOE45 DCOE48 DCOE48 DCOE/SP50 DCOE/SP55 DCOE/SP Verify that your carburetor uses the F8 idle jet specification and confirm the required numerical size before ordering. Compare the replacement with the removed jet and check the overall geometry, threaded interface, seating arrangement and passage configuration. The external geometry has been adapted for broad compatibility with original and aftermarket idle jet holders. Nevertheless, the replacement should always be compared directly with the removed component before installation. The numerical jet size and the F8 air-bleed calibration must both correspond to the intended idle and progression-circuit setup. The illustrated part carries a 45 F8 marking, where 45 identifies the fuel jet size and F8 identifies the richness / air-bleed characteristic. Do not select an idle jet based only on carburetor model. Engine displacement, venturi size, camshaft specification, ignition setup, fuel type and the rest of the carburetor calibration can all influence the required jet size.What you see is what you getShow all parts
