Mikuni Bs25 Carburetor Diagram Patched [repack] May 2026

You're looking for a detailed diagram of the Mikuni BS25 carburetor, specifically a patched or modified version. I'll provide you with some general information and point you in the right direction.

Components and Parts

Why the original diagram fails:

Intake bell/air filter flange — mounts to airbox or pod filter. Check for torn boots causing leaks.
Top cap / air screw area — contains pilot (air) screw on many small Mikuni models; on BS25 this is idle mixture screw (adjusts low-speed mixture).
Slide (throttle valve) — cylindrical slide that rises with cable tension; inspect for scoring and sticky action.
Needle jet & main jet assembly — main jet threads into the needle jet; controls high-speed fuel metering.
Needle (jet needle) & clip positions — tapered needle fits into needle jet; clip height changes mid-range mixture.
Carburetor body / venturi — contains throttle slide and houses pilot jet area; check for vacuum/overflow passages.
Float bowl (bottom) — holds fuel reservoir; gasketed; contains float and float valve (needle valve).
Float — foam or metal; controls fuel level via float valve; check for leaks or incorrect orientation.
Float valve (needle/seat) — seals fuel inlet; common wear point causing flooding.
Pilot (idle) jet — small orifice supplying fuel at idle and low throttle.
Choke / enrichener (if fitted) — enriches mixture for cold starts; some BS25 variants use a slide or plunger.
Fuel inlet fitting — where fuel hose attaches; may have a grommet or banjo fitting.
Overflow/drain screw — allows bowl to drain; useful for compression or leak diagnosis.
Vacuum/vent ports — routing for tick-over or emissions on some applications; blocking or plugging can alter running.
Throttle cable connection / cam — link to slide; inspect for correct routing and free movement.
Idle speed screw — limits closed position of slide to set engine idle RPM.
Bowl drain screw — used to empty bowl during service.

Patched or Modified Diagram