Spray carb cleaner through every hole in the carb body. You should see fluid exiting from another hole. If not, it’s blocked.
For general Mikuni cleaning and deep-service tips that go beyond the basic factory manual, the XJBikes "Church of Clean" thread is widely considered the "gold standard" for vintage Mikuni maintenance. Service Tips mikuni bds26 service manual
The BDS26 has very narrow passages that clog easily with old, "varnished" fuel. Spray carb cleaner through every hole in the carb body
| Symptom | Likely Cause (per manual) | |--------|----------------------------| | Rough idle, one pipe cold | Clipped diaphragm or vacuum leak at that throat’s manifold seal | | Hesitation off-idle | Accelerator pump timing or nozzle clog | | Hard cold start | Enricher plunger not fully sealing (or cable slack) | | Rich surge at cruise | Needle clip too low (rich) or float height too high | | Poor hot restart | Fuel boiling – missing heat spacer gasket or low float | For general Mikuni cleaning and deep-service tips that
The BDS26 is a masterpiece of mechanical fueling, but its complexity and scarcity of parts mean a Without the vacuum sync procedure, float height nuance, and diaphragm handling warnings, the carburetor rapidly becomes an unreliable “boat anchor.”