Hold the rubber slide diaphragm up to a bright light. If you see any light through the rubber, it must be replaced.
Carefully unscrew the Main Jet and the recessed Pilot Jet . Use a precisely fitting flathead screwdriver to avoid stripping the soft brass. mikuni bs26 carburetor manual verified
| Symptom | Probable cause | Manual verification step | |---------|----------------|---------------------------| | Hesitation at 5000 rpm | Torn diaphragm | Visual inspection; blow lightly into vacuum port—slide must rise smoothly | | Hard start cold | Clogged starter circuit | Remove starter plunger; check tiny fuel passages with carb cleaner | | Rich idle (black plugs) | Pilot screw too far in | Reset to 2.5 turns out; replace pilot jet if >3.5 turns required | | Surge at steady throttle | Incorrect float height | Remeasure at 30° angle; adjust tang gently | | High idle (1800+ rpm) | Vacuum leak or stuck slide | Spray propane around intake boots; check slide for free movement | Hold the rubber slide diaphragm up to a bright light
: Supplies a rich mixture for cold engine starts. 🔧 Step-by-Step Tuning Guide Use a precisely fitting flathead screwdriver to avoid
Typically 17mm to 18.5mm (measured from the gasket surface to the top of the float without compressing the spring). 3. Step-by-Step Cleaning & Inspection
| 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 |
Standard operating idle is typically between 1,450 and 1,550 RPM once the engine has reached operating temperature. Maintenance and Rebuild Best Practices