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| Symptom | Likely cause | Fix | |---------|--------------|-----| | Hard start cold | Clogged pilot jet | Clean or replace pilot jet | | Hesitation off-idle | Lean pilot circuit or vacuum leak | Clean pilot + check intake boots | | Won't idle | Pilot screw misadjusted, dirty pilot jet | Reset screw (2.5 turns), clean | | Bogs at WOT | Main jet too small or float low | Rejet or raise float level | | Rich black smoke | Main jet too large, float high, stuck choke | Inspect float height, choke plunger | | Fuel drips from overflow | Stuck needle valve, high float level | Clean or replace needle/seat | | Diaphragm tear | Age, backfires | Replace diaphragm (no repair) | | Runs rich on decel | Coasting enricher stuck open (if fitted) | Inspect valve and diaphragm |
The Mikuni BS26 carburetor represents a balance of performance, economy, and user-friendliness. While it lacks the razor-sharp throttle response of a racing flat-slide carburetor, its design is ideal for street motorcycles where reliability and fuel economy are paramount. Proper understanding of the CV mechanism is essential for diagnostics; most issues stem from idle circuit blockages or diaphragm wear rather than mechanical failure of the body itself. With regular cleaning and correct float adjustment, the BS26 provides thousands of miles of trouble-free operation. mikuni bs26 carburetor