Bs25 Carburetor Diagram [verified] | Mikuni
The float rises with fuel level, closing the needle valve at the preset height (typically 15–17mm measured from bowl mating surface to float top).
The Mikuni BS25 carburetor diagram typically includes the following components:
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Carburetor - Mikuni BS25 Series Round Slide - VMC Chinese Parts
: Because the pilot jet has the smallest passageways, it is the first to clog from old or ethanol-blended fuel, causing hard starting or poor idle. The float rises with fuel level, closing the
Often located on the bottom or side, typically near the engine intake side. It regulates the air-fuel mixture at idle. Idle Speed Screw:
Mikuni BS25 is a Constant Velocity (CV) carburetor commonly found on 125cc to 150cc 4-stroke engines, such as the GY6 series used in various scooters and ATVs. Because it is a CV-style carburetor, it uses engine vacuum to lift a diaphragm and slide rather than a direct mechanical cable connection. Mikuni BS25 Components Breakdown Often located on the bottom or side, typically
to understand how different circuits (pilot, needle, main) interact across the throttle range. specific jet sizes for a certain altitude, or do you need help troubleshooting a specific issue like a high idle or bogging? Carburetor - Mikuni BS25 Series Round Slide
[Air Filter Side] [Engine Side] | | v v +---------+ +--------+ +----------------+ +---------+ | Diaphragm|----->| Throttle|----->| Needle Jet |----->| Intake | | Cover | | Piston | | (Emulsion Tube) | | Boot | +---------+ +--------+ +----------------+ +---------+ | | v v +---------+ +-----------+ +-------------+ | Choke |----->| Float Bowl |<-------| Main Jet | | Plunger | | (Fuel | | (Primary | +---------+ | Reservoir)| | Fuel) | +-----------+ +-------------+ ^ | +-------------+ | Pilot Jet | | (Idle/Off- | | Throttle) | +-------------+
: The vacuum-operated slide (piston valve) houses the jet needle . Changes in engine vacuum pull the diaphragm, lifting the slide and needle to regulate the air-fuel mixture. The Metering Circuit : Main Jet : Controls fuel flow from 3/4 to full throttle. Pilot Jet : Responsible for idle up to 1/4 throttle.