Based on the Mikuni BS25 round slide carburetor Go to product viewer dialog for this item. (commonly used on 150cc GY6 engines), Mikuni BS25 Exploded View & Components
Warning: Do not download random EXE files. Look for image hosts (Imgur, Flickr) or scanned PDFs from reputable forum members. mikuni bs25 carburetor diagram patched
Based on typical BS-series CV carburetor diagrams, these are the primary parts you will find: Upper Section (Vacuum Chamber): Top Cover: Based on the Mikuni BS25 round slide carburetor
The Problem: After 20+ years, the rubber diaphragm cracks, the pilot jet clogs, and the gasket between the float bowl and main body swells or shrinks. Air jet Pilot jet Main jet Needle valve
While a full rebuild kit is the gold standard, many riders look for "patches" to get back on the road quickly.
that identifies specific components and repair solutions for common failure points. VMC Chinese Parts Mikuni BS25 Components & Diagram Guide
The Mikuni BS25 is a constant-velocity (CV) carburetor, a design distinct from the more rudimentary slide carburetors. In a standard diagram, the BS25 appears as a labyrinth of passages, jets, and diaphragms. The defining feature is the vacuum-operated slide. Unlike a mechanical slide that moves directly with the rider’s throttle hand, the BS25 slide is lifted by the pressure differential created by engine vacuum. This results in a smoother throttle response and better fuel economy, as the carburetor automatically compensates for changes in air demand. However, a standard diagram only tells half the story; it presents the ideal, not the reality of a machine that has weathered years of use.