Controls fuel delivery from idle up to 1/4 throttle.
The starter motor churned. Once. Twice. On the third rotation, the engine barked to life, settling into a high, smoky idle. Silas let it warm up for a few minutes, watching the heat bloom off the exhaust header. Then came the real test.
The factory diagram assumes a stock airbox. Many riders install a high-flow (K&N style) air filter or pod filter. This increases airflow, causing the engine to run dangerously lean (too much air, not enough fuel). mikuni bs25 carburetor diagram patched
The Mikuni BS25 is a 25mm round slide carburetor, commonly used in and certain Yamaha or Suzuki small-displacement bikes. Essential Resources & Diagrams
Follow this systematic approach to clean, patch, and rebuild your Mikuni BS25. Step 1: Disassembly and Inspection Controls fuel delivery from idle up to 1/4 throttle
Typically situated on the side of the carburetor body, midway between the top cap and the float bowl. It is a brass or aluminum ribbed fitting.
Whether you’re rebuilding a barn-find GN250 or diagnosing a stubborn idle on a 250 Virago, this patched Mikuni BS25 diagram provides the corrected circuit paths that factory manuals often leave ambiguous. Save it to your shop notes. Then came the real test
: Meter fuel under different throttle openings.