The idle jet is installed under the jet cover on the Weber DCOE series and 45 MCHH carburetors. The F designation indicates that this jet controls both air (side inlet hole) and fuel (inlet hole at the tip). The F number refers to air control, and the size number refers to fuel flow. Two idle jets are required per carburetor (one for MCHH). Sold individually.
Note that Weber assigned F numbers chronologically, as they designed the jets. They do not follow a linear "richest to leanest" sequence. The F11 allows air in through a single 1.20mm bleed hole in the side, while fuel flows through a small 1.5mm internal bore. This makes it the leanest family of idle jets we currently offer. The size numbers do follow a linear sequence, with larger numbers allowing a richer idle mixture. If you are starting from scratch, the experts recommend starting with 45 idle jets for 1600cc, 55 for 2.0L, and 65 for 2.5L engines (assuming dual carbs on a 4-cylinder engine).
DCOE idle jets, listed in order from richest to leanest air bleed:
F6 DCOE Idle Jet (Part No. 74819): Single 0.70mm air bleed
F9 DCOE Idle Jet (Part No. 74822): Single 1.00mm air bleed
F8 DCOE Idle Jet (Part No. 74821): Single 1.20mm air bleed (large fuel bore)
F11 DCOE Idle Jet (Part No. 74824, this jet): Single 1.20mm air bleed (smaller fuel bore)
Note: Fits genuine Weber (made in Italy or made in Spain) carburetors only! Does not fit most copies, Asian knock-offs, or work-alikes.
