Remove the top cap (4 screws). Carefully lift out the vacuum piston/diaphragm assembly. Do not use solvent on the diaphragm. Use only soapy water. Soak the metal body in carb cleaner for 4 hours, but remove all rubber first. 2. Inspecting the Diaphragm Hold the diaphragm up to a light. Any pinholes or cracking means replacement. The manual includes a “stretch test” – the diaphragm should return to flat within 2 seconds after being folded. 3. Setting the Float Height The BDS26 manual shows an inverted carburetor method. With the gasket in place, measure from the float bowl mating surface to the highest point of the float. Spec: 15mm ± 1mm . Bend the float tang carefully. Incorrect float height is the #1 cause of flooding on the BDS26. 4. Jetting Chart Reference A typical page in the BDS26 service manual will list:
These are example values – refer to your specific manual for your engine model. If your engine uses two BDS26 carbs (common in twin-cylinder snowmobiles), the service manual includes a synchronization procedure using a manometer or a drill bit method. The goal: both slides begin to move at exactly the same throttle opening (typically 0.5mm gap at idle). Common Troubleshooting Guide (From the Manual) The official Mikuni BDS26 service manual has a dedicated troubleshooting matrix. Here are the highlights: mikuni bds26 service manual
If you have landed on this page, you are likely staring at a vintage carburetor with “Mikuni BDS26” stamped on the side. Whether it is bolted to a classic Arctic Cat snowmobile, a vintage Yamaha Enticer, or a custom go-kart, one truth remains universal: you cannot properly service this carburetor without a dedicated Mikuni BDS26 service manual. Remove the top cap (4 screws)
The is more than a paperweight—it is a precision tool. It provides the tolerances, jetting data, and vacuum circuit maps that no YouTube tutorial can fully replace. Bookmark a reliable PDF source, print the critical pages (float height, jetting chart, exploded view), and keep them in your shop. Use only soapy water
In this article, we will explore everything you need to know about locating, using, and understanding the BDS26 service manual. We will cover common issues, exploded parts views, torque specifications, jetting charts, and step-by-step maintenance procedures that are typically found only in the official documentation. Before diving into the manual, let’s establish the hardware. The Mikuni BDS26 is a diaphragm-type (constant velocity) carburetor with a 26mm bore. Unlike traditional slide carburetors, the BDS series uses engine vacuum to lift the slide, offering smoother throttle response in variable load conditions like deep snow or uneven terrain.
| Temperature | Altitude | Main Jet | Pilot Jet | Air Screw (turns out) | |-------------|----------|----------|-----------|------------------------| | -10°C to 0°C | 0-3000ft | 135 | 25 | 1.75 | | 0°C to 10°C | 3000-6000ft | 130 | 22.5 | 2.0 | | 10°C+ | 6000ft+ | 125 | 20 | 2.25 |