Mikuni Bs25 Carburetor Diagram Patched //top\\ Jun 2026

The BS25 has a small barbed fitting for the fuel petcock (auto fuel valve).

Apply an ultra-thin layer over the tear using a toothpick. Keep it as thin as possible so the rubber remains flexible.

With the engine idling, slowly turn the screw clockwise (leaner) or counter-clockwise (richer) by 1/4-turn increments. Listen closely to the engine speed. Find the exact position where the engine idles at its highest, smoothest RPM. mikuni bs25 carburetor diagram patched

Based on your specific motorcycle, write down the known-good baseline settings.

A brass screw-in restriction that dictates fuel delivery from 75% to 100% wide-open throttle. The BS25 has a small barbed fitting for

Rubber diaphragms flex millions of times. Glue hardens. Within 100 miles, that patch will crack, and you’ll be back to square one—only now with glue residue ruining the slide channel.

Misrouting vacuum and fuel lines is the most common mistake during a carburetor rebuild. Use this reference map to identify and route every external port on the Mikuni BS25. With the engine idling, slowly turn the screw

Original: Shows the diaphragm as a simple rubber disc. A close-up inset showing the alignment tab inside the carb cap channel. If misaligned (often by 180 degrees), the slide won’t lift. The patched diagram colors this tab in green.

: Meters the volume of fuel at closed throttle.