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Remove the main jet and pilot jet using a flathead screwdriver that fits perfectly to avoid stripping the brass.
You can find detailed exploded views and parts lists through these authoritative sources:
The definitive patch requires a multi-step sealing and reinforcement process:
Seals the fuel reservoir to prevent external leaks. mikuni bs25 carburetor diagram patched
: Meter fuel under different throttle openings.
Remove the carburetor. Remove the bowl, float, needle, and jets. Spray all passages with carburetor cleaner. Use compressed air, not wire, to clean jets, as wire can change the jet diameter.
When rebuilding a BS25:
However, searching for a standard exploded view often leads to confusion. You may have stumbled upon the term This is not an official Mikuni document, but a community-driven modification to the original schematic.
Original: Shows the float valve seat screwing directly into the carb body. A yellow highlight showing the tiny deformed o-ring (Part# 34 in most lists) that lies behind the seat. The patched diagram often includes a handwritten note: "Change this O-ring FIRST for flooding."
Clean the gasket groove thoroughly. If the gasket is stretched, use a razor to trim a small section and use specialized fuel-resistant sealant (e.g., Yamabond 4 or Hondabond) to seal the gap between the bowl and the body. Area 3: Pilot Jet Clogs (The "Stuck" Jet) Remove the main jet and pilot jet using
: Mechanically props open the butterfly valve to set resting RPM. Anatomy of the Four Essential Fuel Circuits
: Controls the airflow and needle height based on engine vacuum.