This screw is often hidden under a brass plug to prevent tampering for emissions compliance. Before removing the plug, mark its exact starting position. On the BS26, this screw is typically a , meaning that turning it out (counter-clockwise) enriches the idle mixture , and turning it in (clockwise) leans it out. A common baseline is 2 turns out from lightly seated .
Provides a richer mixture for cold starts. Key Components of the BS26: Diaphragm/Slide: Creates the CV effect. Main Jet: Determines high-RPM fueling. Pilot Jet/Screw: Controls idle mixture. Jet Needle: Adjustable to fine-tune midrange (5 notches). 2. Verified Mikuni BS26 Tuning & Adjustment Procedure
The BS26 is a slide-type carburetor where a diaphragm, reacting to vacuum pressure, lifts the slide and needle. Controls fuel from idle to 1/4 throttle. Needle/Needle Jet: Controls fuel from 1/4 to 3/4 throttle. Main Jet: Controls fuel from 3/4 to full throttle.
Reinstall the float and needle valve. Invert the carburetor body so the float rests gently against the needle valve without compressing the tiny, internal spring-loaded pin. Measure the distance from the mixing chamber gasket surface (without the gasket) to the top of the float. Adjust it to 21.4 mm by carefully bending the small metal tang on the float arm.
0% Throttle 25% Throttle 50% Throttle 100% Throttle │ │ │ │ ▼ ▼ ▼ ▼ [ Pilot Screw ] ─── [ Pilot Jet ] │ ▼ [ Needle Jet / Clip ] ──────────────────── [ Main Jet ] Adjusting the Pilot Fuel Screw mikuni bs26 carburetor manual verified
This design prevents the engine from bogging down if you snap the throttle open quickly at low RPM. Complete Specifications Factory Standard Specification Main Jet #110 to #132.5 (Application dependent) Pilot Jet (Idle) #15 to #22.5 Pilot Screw 1.5 to 2.5 turns out from lightly seated Float Height 17.0 mm ± 1.0 mm Step-by-Step Disassembly
Mikuni BS26 Carburetor Manual Verified: Complete Tuning & Service Guide
Affects mid-range, partial throttle. Float & Float Needle: Regulates fuel level in the bowl. Idle Speed Screw: Adjusts idle RPM. Pilot Air/Fuel Screw: Fine-tunes low-end mixture. 3. Verified Tuning and Adjustment Procedures Proper tuning is essential for a smooth-running engine. A. Pilot Air/Fuel Screw Setting (Initial)
Connected to the nipple at the very bottom of the float bowl to safely route purged fuel away from the engine. 5. Precise Tuning and Adjustments Measuring and Adjusting Float Height This screw is often hidden under a brass
Remove float bowl, extract pilot jet, clear passage with solvent and compressed air. Dirty inlet valve seat or incorrect float height setting.
If you want to troubleshoot a specific issue with your Mikuni BS26, I can provide the exact steps. Please let me know: The of your vehicle
Use a dip basket or specialized cleaner for stubborn varnish, but always remove rubber gaskets and O-rings first to prevent swelling. Blow out all orifices with compressed air after soaking.
What of vehicle is this carburetor installed on? A common baseline is 2 turns out from lightly seated
This creates a consistent air velocity, reducing "bogging" and providing smoother throttle response at low-to-mid RPMs. 2. Key Components Checklist (Verified Layout)
Inspect the rubber tip of the float needle. If it has a grooved ring worn into the cone, it will leak fuel and must be replaced.
Starting point is generally 1.5 to 2 turns out from lightly seated. Service & Maintenance Guide
The Mikuni BS26 is a 26mm constant velocity (CV) carburetor. It controls fuel delivery on many small-displacement motorcycles, ATVs, and scooters. This manual details how to strip, clean, tune, and rebuild your Mikuni BS26 carburetor. Understanding the CV System
The Mikuni BS26 carburetor is a popular and highly-regarded carburetor used on a variety of motorcycles, scooters, and other small engines. Known for its reliability and performance, the BS26 has become a favorite among enthusiasts and mechanics alike. In this article, we'll provide a comprehensive manual for the Mikuni BS26 carburetor, including specifications, troubleshooting tips, and maintenance procedures.