Understanding the Mikuni BDS26 Carburetor The is a dual-body, downdraft constant velocity (CV) carburetor, most famously used as original equipment on motorcycles like the Yamaha Virago XV250 . Unlike direct-slide carburetors, the BDS26 uses atmospheric pressure differentials to move the throttle slide, providing smoother power delivery and better fuel economy for small-to-mid-sized engines. 1. Key Components and Function A standard service involves three primary systems:
Standard sizes range from #87.5 to #90 depending on the cylinder (front/rear). Pilot Jet: Typically #20.
October 26, 2023 Subject: Operational Overview, Maintenance Procedures, and Tuning Specifications for Mikuni BDS26 Carburetor Target Application: Small Displacement Motorcycle Engines (typically 125cc–150cc) mikuni bds26 service manual
Often caused by worn gaskets or a failing needle valve seat.
Always use new O-rings on the pilot screw and fuel joint pipes. Understanding the Mikuni BDS26 Carburetor The is a
Remove the top cap to inspect the rubber diaphragm. Look for tears, cracks, or hardening. 5. Rebuilding and Reassembly
Often indicates a vacuum leak (check the intake boots) or a lean pilot circuit. Key Components and Function A standard service involves
Hold the carburetor body at a 45-to-60-degree angle so the float arm rests lightly against the needle valve spring plunger without compressing it.
Use a flathead screwdriver to remove the Main Jet and the Pilot Jet. The Pilot Jet is often recessed in a deep hole—ensure your screwdriver fits perfectly to avoid stripping the brass. Step 2: Deep Cleaning
Flip the carburetor upside down. Remove the four screws holding the float bowl.
The Mikuni BDS26 is a dual-body, downdraft constant velocity (CV) carburetor widely used on small-to-medium displacement motorcycles, ATVs, and cruisers—most notably the Yamaha Virago XV250 (V-Star 250). Known for its reliability under optimal conditions, a BDS26 that has sat with modern ethanol fuel will suffer from clogged jets, torn diaphragms, and stiff o-rings.