Weber IDF Idle Jet 70, for Idf & HPMX

OVERVIEW

Precision tuning is the heartbeat of a high-performance air-cooled Volkswagen engine, and nothing dictates your off-the-line responsiveness and low-end drivability quite like the idle circuit. The Weber IDF Idle Jet 70 is a critical component for enthusiasts running Weber IDF or EMPI HPMX dual carburetor setups. While often misunderstood as only affecting the engine at a standstill, the idle jet actually governs the fuel delivery from idle all the way through the progression phaseroughly up to 2,500 or 3,000 RPM. If your engine suffers from annoying "flat spots" or hesitates when you lightly step on the gas, moving to a .70 jet might be the exact solution needed to richen the mixture and provide a seamless transition to the main circuit. At Appletree Auto, we know that generic tuning leads to generic performance, which is why we provide genuine-spec brass jets to ensure your air-fuel ratio is spot-on for your specific displacement and camshaft profile.

Crafted from high-quality brass for maximum corrosion resistance and dimensional stability, these jets are engineered to hold their tolerance even under the heat and vibration of a high-revving flat-four. The .70 size is particularly popular for larger displacement engines or those running in cooler climates where a slightly richer idle mixture helps prevent the dreaded "lean pop" through the carburetors. Whether you are dialing in a street-thumping 1914cc or a weekend-warrior 2276cc, having a set of these jets in your tuning kit is essential. Don''t settle for a "close enough" tune that leaves your VW feeling sluggish or running hot; upgrade your IDF or HPMX carburetors with these precision-machined jets and experience the crisp, immediate throttle response that makes driving a classic VW so rewarding.

FITMENT

This idle jet is designed for a wide range of air-cooled applications and performance carburetor configurations, including:

• Weber IDF Carburetors: Compatible with 40 IDF, 44 IDF, and 48 IDF models.
• EMPI HPMX Carburetors: Compatible with 40mm and 44mm HPMX series.
• VW Type 1 Beetle/Bug: All years when equipped with dual IDF/HPMX setups.
• VW Type 2 Bus/Transporter: Ideal for high-performance upright or pancake engine conversions.
• VW Type 3 Fastback/Squareback: Fits dual-carbureted performance builds.
• VW Karmann Ghia: Fits all models utilizing dual Weber or HPMX induction.
• VW Thing (Type 181): Perfect for off-road or street performance upgrades.
• Custom Sand Rails and Bajas: Essential for fine-tuning engines in varying altitudes and conditions.

SPECS

• Jet Size: .70 (0.70mm Orifice).
• Material: Precision-Machined Solid Brass.
• Carburetor Compatibility: Weber IDF & EMPI HPMX.
• Circuit Type: Idle and Progression Circuit.
• Thread Type: Standard Weber Idle Jet Threading.
• Finish: Natural Brass.
• Quantity: Sold Individually (Most dual-carb setups require four total).

PRO TIPS

1. Diagnosing the Progression Flat Spot

If your VW feels like it "stumbles" or "bogs" when you are slowly accelerating from a stop sign, but then takes off once the RPMs get high, your idle jet is likely too small. The idle jet handles the "progression" stage where the throttle plate uncovers the tiny holes in the throat of the carburetor. A .70 jet provides more fuel during this critical window than a standard .50 or .55 jet. If you hear a "pop" back through the carburetor intake during light acceleration, that is a classic lean condition. Swapping to a .70 can often eliminate that lean pop and make your VW much more pleasant to drive in stop-and-go traffic.

2. Never Use Wire to Clean Your Jets

It is tempting to grab a thin piece of safety wire or a needle to clear a clog in an idle jet, but you should never do this. Brass is a relatively soft metal, and even a tiny scratch or slight enlargement of the orifice from a wire can completely change the flow characteristics of the jet. A .70 jet can quickly become a .75 or worse if you aren''t careful. Always use pressurized aerosol carburetor cleaner and compressed air to blow out debris. If the jet is heavily tarnished or clogged with old fuel, soak it in a dedicated carb cleaning solution rather than using mechanical force.

3. Sync Your Carbs Before Final Jetting

Before you decide that you definitely need a different idle jet, ensure your carburetors are perfectly synchronized with a high-quality Uni-Syn or snail-type flow meter. If one carburetor is drawing more air than the other at idle, it will mimic the symptoms of a lean or rich jetting issue. Once your linkage is balanced and your air-bypass screws are set, then you can accurately evaluate if the .70 idle jet is providing the correct mixture. Remember, the idle mixture screw on the side of the carb only controls the volume of the mixture already "pre-mixed" by this jet, so getting the jet size right is the foundation of the entire tune.