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Carburetors & Jets

Motorcycle Carburetors, Jet Kits & Carburetor Components

The carburetor is one of the most elegantly simple and most precisely calibrated components on any motorcycle. It has no electronics, no sensors, and no computer control. It uses nothing but the physics of airflow and fuel pressure to meter exactly the right amount of fuel into the engine at every throttle position across the entire operating range. When it is clean, correctly jetted, and properly adjusted, a well-built carburetor delivers crisp throttle response, reliable starting, and consistent power that a poorly calibrated fuel injection system cannot always match. When it is dirty, worn, or incorrectly jetted for the current conditions, no amount of other tuning work will make the engine run right until the carburetor is addressed.

Carbureted motorcycles remain the dominant configuration across two-stroke motocross and enduro bikes and across a significant portion of the older four-stroke machines that make up a large part of the riding population. Understanding how to maintain, rebuild, and correctly jet a carburetor is one of the most valuable skills any motorcycle owner can develop, and having access to the right carburetor components makes that work straightforward and rewarding. Mad Lads Moto stocks carburetors, jet kits, rebuild kits, and individual carburetor components for two-stroke and four-stroke motorcycles across all major makes and models. Here is what we carry:

  • Complete Carburetors - OEM-spec replacement carburetors for machines where the stock carburetor has worn beyond rebuilding, sustained physical damage, or where a complete replacement is more practical than an extensive rebuild of a high-hour unit.
  • Carburetor Rebuild Kits - Complete rebuild kits including all jets, needles, float valves, diaphragms, gaskets, and O-rings needed to restore a worn or varnish-damaged carburetor to full function without replacing the entire unit.
  • Main Jets - Individual main jets in a full range of sizes for altitude and temperature tuning on carbureted two-stroke and four-stroke motorcycles where the main jet controls fuel delivery at three-quarter to full throttle.
  • Pilot Jets - Individual pilot jets and slow jets in a range of sizes for idle and low-throttle fuel delivery tuning on carbureted motorcycles where pilot circuit calibration affects starting, idle quality, and low-speed response.
  • Jet Kits - Complete jet kits that include a range of main jets, pilot jets, and in some cases needles and needle clips for comprehensive carburetor tuning across a range of altitude and temperature conditions without ordering individual jets one at a time.
  • Needles & Needle Jets - Carburetor needles and needle jets that control fuel delivery in the mid-throttle range between one quarter and three quarter throttle where most real-world riding happens and where needle calibration has the greatest effect on throttle response, fuel economy, and mid-range power delivery.
  • Float Valves & Floats - Replacement float valves, needle valves, and float assemblies for carburetors where the float valve has worn and is allowing fuel to overflow or where the float has developed a leak that affects fuel level regulation in the bowl.
  • Throttle Slides & Diaphragms - Replacement throttle slides, slide diaphragms, and slide components for CV carburetors where the slide or diaphragm has worn or cracked and is affecting throttle response and fuel delivery consistency.
  • Air Screws & Pilot Screws - Replacement air screws, fuel screws, pilot screws, and extended adjustable fuel screws that allow fine-tuning of the pilot circuit mixture without removing the carburetor from the engine.

Jetting a carburetor correctly for your altitude and temperature conditions is one of the most important and most commonly neglected aspects of motorcycle maintenance for riders who travel to different elevations for riding. The standard starting point for altitude jetting is to go one main jet size leaner for every 2000 feet of elevation gain above the elevation where the carburetor was originally jetted, because thinner air at altitude contains less oxygen and requires less fuel to maintain the correct mixture ratio. Temperature affects jetting in the opposite direction: colder air is denser and contains more oxygen, requiring slightly richer jetting than the same elevation in warm conditions. A spark plug reading after a hard run at a new elevation is the most reliable real-world confirmation of whether your jetting is correct before committing to more riding on the new setup. We stock carburetor components for Honda, Yamaha, Kawasaki, Suzuki, KTM, Husqvarna, Beta, GasGas, and more. Use our year, make, and model fitment tool to confirm fitment before you order.

How do I clean a motorcycle carburetor without removing it from the bike?

Cleaning a carburetor without full removal is possible for mild varnish deposits and contamination but has limitations compared to a complete disassembly and cleaning. With the carburetor on the bike, drain the float bowl by loosening the drain screw and allow the bowl to empty completely. Remove the float bowl and spray carburetor cleaner into the bowl area and through the visible jet passages, using the straw attached to the cleaner can to direct the spray into small passages. Reinstall the float bowl with a new gasket if the original has been disturbed, then run the engine and rev it through the RPM range to flush loosened deposits through the fuel system. This approach works well for mild contamination from short-term storage. For carburetors with significant varnish buildup in the main jet, pilot jet, needle jet, and emulsion tube passages, a complete removal and ultrasonic cleaning or thorough manual cleaning with proper carburetor cleaner and compressed air through all passages is the only approach that reliably restores full function.

How do I read a spark plug to check my carburetor jetting?

Reading a spark plug to evaluate carburetor jetting requires a fresh plug installed in the engine, a hard run at the throttle opening you want to evaluate, and an immediate engine shutdown by killing the ignition rather than closing the throttle, so the plug color reflects the mixture at that throttle position without being washed by the lean condition of deceleration. Remove the plug immediately after shutdown and examine the insulator tip around the center electrode. A tan or light brown color indicates a correct mixture. A white or light gray color indicates a lean condition that requires a richer jet or needle position. A black, sooty, or wet appearance indicates a rich condition that requires a leaner jet or needle position. The main jet is best evaluated with a full throttle run followed by an immediate shutdown. The pilot circuit is best evaluated with an idle and low throttle run. The needle affects mid-throttle and is evaluated with a half-throttle run. Each circuit requires a separate plug reading for accurate evaluation.

What is an extended fuel screw and do I need one on my four-stroke dirt bike?

An extended or adjustable fuel screw replaces the stock pilot circuit fuel screw on a four-stroke carburetor with a larger, easier-to-access version that can be adjusted by hand or with a simple tool without removing the carburetor from the bike. The stock fuel screw on most four-stroke carburetors is recessed in a location that requires removing the carburetor or using a specialized short screwdriver to access, making pilot circuit fine-tuning on the trail or at the track impractical. An extended fuel screw moves the adjustment point to a more accessible location and often adds a knurled knob or T-handle that allows adjustment without any tools at all. For riders who travel to different elevations and temperatures where pilot circuit tuning makes a meaningful difference in starting and low-throttle response, an extended fuel screw is a low-cost upgrade that pays for itself the first time you tune the pilot circuit trailside without pulling the carburetor off the bike.
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