Use the idle thumb screw to drop the idle back down to factory specification (typically 1,400 RPM). Resolving Mid-Range Lean or Rich Conditions
A thick brass or plastic T-fitting located between the carburetor body (if dual) or on the side. Connects directly to the fuel tank petcock line.
A thorough cleaning is the most effective fix for most Mikuni BS26 performance issues. Follow these steps for a complete teardown and reassembly. 1. Disassembly & Inspection mikuni bs26 carburetor manual verified
The BS26 is a constant-velocity carburetor, meaning the slide position is not mechanically linked to the throttle grip. Instead, a vacuum port downstream of the throttle valve lifts the diaphragm slide against spring pressure.
“The BS26 main jet can be changed without removing the carburetor.” Use the idle thumb screw to drop the
The information provided in this manual has been verified and validated through various sources, including:
Before diving into the manual, it's essential to familiarize yourself with the components and specifications of the Mikuni BS26 carburetor. The main components include: A thorough cleaning is the most effective fix
If you have to back the screw out more than 3 turns to get a smooth idle, your pilot jet is too small or restricted. If it requires less than 1 turn out, your pilot jet is too large. 6. Troubleshooting Common Symptoms Probable Cause Corrective Action Torn vacuum diaphragm or clogged main jet. Replace diaphragm or clear main jet passages. Fuel leaks from the overflow hose Dirty needle valve or incorrect float height.
Starting point is generally 1.5 to 2 turns out from lightly seated. Service & Maintenance Guide
This verified manual and technical guide provides everything you need to service, clean, tune, and troubleshoot your Mikuni BS26 carburetor. 1. Technical Specifications and Factory Jetting Standard Factory Specification Main Jet (MJ) #95 to #102.5 (Varies by model) Pilot Jet (PJ) #12.5 to #15 Jet Needle (JN) 4DJ21 (Multi-groove or fixed) Float Height 21.4mm ± 1.0mm Idle Speed 1,300 – 1,500 RPM Pilot Screw Position 1.5 to 2.25 turns out 2. Component Diagram & Exploded View Breakdown