Brosol/Solex Main Jets 120

Precision Fuel Tuning with EMPI Brosol/Solex 120 Main Jets

When it comes to the heart of your air-cooled Volkswagen, the carburetor dictates exactly how your engine performs under load, at cruise, and during acceleration. These EMPI Brosol/Solex 120 main jets are the essential component for any VW enthusiast looking to achieve the perfect stoichiometric balance. Every air-cooled engine is a unique beast, influenced by its displacement, compression ratio, camshaft profile, and even the local weather. If your engine is suffering from a mid-range stumble or is running dangerously lean after installing a high-flow exhaust or a generic air cleaner, swapping to a 120 main jet can provide the additional fuel volume needed to stabilize your air-fuel ratio. These jets are precision-manufactured to ensure consistent flow rates, which is critical for preventing localized hot spots on your pistons and valves that can lead to catastrophic engine failure. By fine-tuning your fuel delivery with these high-quality brass components, you aren''t just improving performance; you are investing in the longevity of your vintage powerplant.

At Appletree Auto, we understand that "close enough" isn''t good enough when it involves your classic Beetle, Bus, or Ghia. The 120 size main jet is a staple in the tuner''s kit, often serving as the "sweet spot" for 1600cc engines running modern, ethanol-blended pump gas which tends to run leaner than the fuels of the 1970s. Whether you are rebuilding an original German Solex 34 PICT-3 or setting up a brand new Brosol replacement carburetor, these jets offer the threading and taper accuracy required for a leak-free, perfect fit. Don''t settle for "out of the box" settings that leave your VW feeling sluggish or overheating. Taking the time to dial in your jetting allows for crisper throttle response and smoother transitions through the RPM range. These jets are sold individually, allowing you to buy exactly what you need to build your custom jetting assortment for track days, high-altitude mountain climbs, or seaside cruising.

Vehicle and Carburetor Fitment

These main jets are designed for use with stock-style Solex and Brosol carburetors commonly found on the following models:

• VW Beetle: 1950 through 1979 (Standard and Super Beetle)
• VW Karmann Ghia: 1956 through 1974
• VW Bus / Type 2: 1950 through 1971 (with Type 1 upright engines)
• VW Thing / Type 181: 1973 through 1974
• VW Squareback, Fastback, Notchback / Type 3: 1962 through 1973
• Compatible Carburetor Models: Solex 28 PICT, 30 PICT-1, 30 PICT-2, 30 PICT-3, 31 PICT-3, 34 PICT-3, 34 PICT-4
• Aftermarket Carburetor Models: Brosol H30/31, H34, and EMPI EPC 34 series

Technical Specifications and Dimensions

Each jet is manufactured to strict tolerances to ensure repeatable performance across multiple cylinders or carburetor banks.

• Jet Size: 120 (equivalent to a 1.20mm precision-drilled orifice)
• Material: High-grade solid brass for corrosion resistance and thermal stability
• Thread Type: Standard Solex/Brosol metric main jet threading
• Head Type: Slotted for easy installation and removal with a standard flathead screwdriver
• Manufacturer: EMPI
• Part Number: 43-5120-7
• Application: Primary fuel metering for main circuit operation

Expert Pro Tips from the Appletree Shop

Tip 1: The "Plug Chop" Verification

To verify if the 120 main jet is the correct size for your specific engine configuration, perform a "plug chop." Take your VW out to a safe stretch of road, accelerate to a steady cruising speed in 3rd or 4th gear (holding the throttle steady for about 30 seconds), then quickly turn off the ignition and pull over. Remove a spark plug and inspect the porcelain insulator. A light tan or "coffee with cream" color indicates your 120 jet is providing the correct mixture. If the porcelain is stark white, you are running lean and may need a 125 or 130 jet. If it is black or sooty, the 120 is too rich, and you should step down to a 115 or 117.5.

Tip 2: Altitude and Jetting Dynamics

Atmospheric pressure changes your engine''s fuel requirements significantly. If you live at a high altitude (above 4,000 feet), the air is thinner, meaning you need less fuel to maintain the proper ratio. In high-altitude environments, a 120 jet might be too large for a stock 1600cc engine, causing it to run rich and lose power. Conversely, if you are at sea level where the air is dense, the 120 jet is often the perfect upgrade to prevent the engine from running too hot. Always keep a small selection of jets in your glovebox if you plan on driving your VW through significant elevation changes, such as a trip through the Rockies or the Sierras.

Tip 3: Protect the Orifice During Maintenance

Never, under any circumstances, use a piece of wire, a needle, or a welding tip cleaner to clean a brass main jet. Brass is a relatively soft metal, and using a hard tool to "clear" a clog will inadvertently enlarge the 1.20mm hole or create tiny scratches that disrupt the laminar flow of the fuel. This can turn your 120 jet into a 125 or worse, making it impossible to tune the carburetor accurately. If the jet becomes clogged with debris or varnish, soak it in a dedicated carburetor