Mikuni Bs25 Carburetor Diagram Patched Site

Mikuni BS25 — Patched Carburetor Diagram Write-up

Overview

A "patched" Mikuni BS25 refers to a BS-series 25mm carburetor modified to fix common wear or damage (worn throttle shaft, cracked float bowl, damaged vacuum slide boot, etc.) and to restore proper function. This write-up explains the patched diagram, common patches, and how to read the labeled parts so you can verify or reproduce the repair.

Float Bowl: Retains fuel; often contains a 90-degree drain hose. mikuni bs25 carburetor diagram patched

Rebuild Procedure (step-by-step)

1. Remove carburetor and drain fuel.
2. Photograph assembly for reference.
3. Remove float bowl screws and bowl.
4. Remove float and float valve; inspect for wear or fuel inside float.
5. Extract pilot jet, main jet, needle jet, and needle—note clip position.
6. Clean all passages with carb cleaner and compressed air; soak components in carburetor cleaner if needed.
7. Inspect gasket and diaphragms; replace with rebuild kit parts.
8. Reassemble in reverse, set needle clip to original position, set pilot screw to 1.5–2 turns out as baseline, and set float height per spec (typical small BS floats ~6–8 mm; if unknown, measure with caliper and set by bending tang or using shims).
9. Reinstall carb, reconnect fuel and throttle cable, adjust idle speed and mixture on the engine.

’s workshop, but tonight, it was cut by the sharp scent of solder. Spread across his scarred wooden bench was a weathered piece of butcher paper containing the holy grail of his current project: a heavily annotated, hand-corrected schematic of a Mikuni BS25 constant velocity carburetor Go to product viewer dialog for this item. Mikuni BS25 — Patched Carburetor Diagram Write-up Overview

Final tips

• Keep a labeled photo record of disassembly.
• Make one change at a time when tuning.
• Use genuine rebuild parts where reliability matters.
• For significant structural damage, replacing the carburetor is usually safer and cheaper long-term.

refers to a specific, hand-annotated JPG that circulated on sites like ViragoTech Remove carburetor and drain fuel

Install an Inline Filter: Prevent rust from the tank from reaching the delicate needle valve.

Pilot (Slow) Jet & Air Screw: Manages fuel delivery at idle and low speeds. Technical Specifications Intake Side ID/OD: 25mm / 34mm. Air Filter Side ID/OD: 38mm / 42mm.

2. The Taped Vacuum Port

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