| Parameter | Spec | |-----------|------| | | Constant Velocity (CV), downdraft | | Bore size | 26 mm | | Venturi diameter | 24.5 mm (effective) | | Fuel inlet | 5/16" (8mm) barb | | Float bowl gasket | Rubber (O-ring type) | | Pilot air jet | 120–130 (varies by model) | | Main air jet | 180–200 | | Idle speed | 1,200–1,300 RPM |
With the engine idling, turn the screw out 1/4 turn at a time until the idle RPM peaks and stabilizes. If you must turn the screw out more than 3.5 turns to get a smooth idle, your pilot jet is too small. If it requires less than 1 turn, your pilot jet is too large. 6. Verification & Troubleshooting Matrix Probable Cause Verified Solution Torn vacuum diaphragm or lean pilot circuit. Inspect diaphragm for holes; turn pilot screw out 1/4 turn. Fuel leaks from the overflow tube Stuck float needle or incorrect float height. Clean needle valve seat; reset float height to 14.0mm. Engine idles fine but bogs/dies at half throttle Needle clip too low or blocked emulsion tube. Clean emulsion tube orifices; verify needle position. Black smoke from exhaust / Spark plug fouled black Rich mixture, leaking choke plunger, or high float level.
Turn the screw in or out in 1/4-turn increments until you find the highest, smoothest idle speed. mikuni bs26 carburetor manual verified
(per Mikuni manual):
1.5 to 2.0 turns out from seated Component Identification and Overview | Parameter | Spec | |-----------|------| | |
Periodically check the rubber diaphragm for holes, cracks, or stiffness, as these will prevent the slide from lifting correctly. Float Height:
| Circuit | Typical BS26 range | GS500 (1996–2000) | |---------|-------------------|--------------------| | Pilot jet | 35 – 45 | 37.5 | | Main jet | 120 – 140 | 125 | | Pilot air jet | 80 – 120 | 95 | | Needle clip position | Groove 1–5 | 3rd from top | Fuel leaks from the overflow tube Stuck float
Specifically for removing the pilot jet without damaging the slot. Needle-Nose Pliers: For removing the float needle seat.
Use a properly sized screwdriver to avoid stripping the brass. Remove the main jet, pilot jet, and needle seat.