Mikuni Bs25 Carburetor Diagram Patched 💯

The Mikuni BS25 is a constant velocity (CV) carburetor commonly found on small to medium-displacement motorcycles, scooters, and ATVs from the 1980s to early 2000s—notably on Suzuki GN250, TU250, and early Yamaha Virago 250 models. Its design prioritizes smooth throttle response and fuel efficiency, but over time, vacuum leaks and clogged circuits make a clean diagram essential for troubleshooting.

: Some knock-off versions (like the UCAL BS29) may lack a spring or O-ring on the mixture screw, which a patched diagram will often note as a critical reassembly step. mikuni bs25 carburetor diagram patched

| Patch Type | Diagram Marking | Purpose | |------------|----------------|---------| | | Red circle around pilot jet | Replacement with larger jet (e.g., #42.5 → #45) | | Drilled passage | Dashed line added | Enlarging air bleed hole for richer idle | | Gasket repair | Cross-hatched area | Silicone or paper gasket patch for vacuum leak | The Mikuni BS25 is a constant velocity (CV)

Do you have a specific variation of the BS25 (for example, the one with the hot start fitting)? The patches vary by model. Leave your carb’s stamp number (e.g., BS25-13) in the comments below for a custom patch guide. | Patch Type | Diagram Marking | Purpose

The Mikuni BS25 is a featuring a 25mm intake bore. It is commonly found on 150cc 4-stroke engines, such as the GY6, and motorcycles like the Yamaha Lagenda 135LC. Key Components of a BS25 Carburetor