The correct Yamaha G23 carburetor jet depends on the exact engine, carburetor and model year. Read the stamped main and pilot jets and match them to the correct service or parts specification.
G23 • Main & pilot jet sizes
G23 carburetor jet sizes at a glance
Main jet
Use the stamped main jet for the exact Yamaha/Mikuni carburetor ID.
Pilot jet
Use the stamped pilot jet for the exact Yamaha/Mikuni carburetor ID.
Altitude
Use the manufacturer altitude chart where one is published.
Before ordering
Identify the engine and carburetor, then read the number stamped on the existing brass jet.
Lean symptoms
Needing choke, surging or load bog can also come from a clogged passage, weak fuel supply or intake leak.
Rich symptoms
Black smoke or plug fouling can also come from a stuck choke, high float level or leaking needle valve.
How to choose the correct Yamaha G23 jet
G23 jetting symptoms
Needs choke to run
Clean the pilot and main circuits and check fuel supply and an intake leak before fitting a larger jet.
Bogs under load
A restricted main jet can cause this, but so can weak pump flow, low bowl fuel level or a blocked filter.
Black smoke / fouled plug
Check choke position, float level and needle sealing before assuming the main jet is too large.
Runs well only at low speed
Main-jet or main-nozzle restriction becomes more likely once the pilot circuit is known to be clear.
Poor idle only
The pilot circuit matters much more than the main jet at idle.
High-altitude operation
Use the model-specific elevation chart where available; do not guess how many jet sizes to reduce.
G23 jet specifications
Applies to: Carbureted gasoline version.
Engine: Yamaha gasoline; generation varies.
Carburetor: Yamaha/Mikuni carburetor; model-specific.
Main jet: Use the stamped main jet for the exact Yamaha/Mikuni carburetor ID.
Pilot jet: Use the stamped pilot jet for the exact Yamaha/Mikuni carburetor ID.
Altitude: Use the manufacturer altitude chart where one is published.
Model-specific note
Yamaha G23 carburetors changed across production years. Match the carburetor ID and existing jet markings before ordering.
Yamaha G23 carburetor jet FAQ
What is the Yamaha G23 main jet size?
Use the stamped main jet for the exact Yamaha/Mikuni carburetor ID. Yamaha G23 carburetors changed across production years. Match the carburetor ID and existing jet markings before ordering.
What is the Yamaha G23 pilot jet size?
Use the stamped pilot jet for the exact Yamaha/Mikuni carburetor ID.
Does altitude change the Yamaha G23 main jet?
Use the manufacturer altitude chart where one is published.
Can I install a larger jet in a Yamaha G23?
Only after confirming the engine, carburetor, altitude and cause of the lean symptom. A clogged passage, intake leak or weak fuel supply should not be corrected with an oversized jet.
How do I identify the correct Yamaha G23 carburetor jet?
Use the stamped jet number together with the engine code, carburetor ID and model year. Cross-check those identifiers against the matching factory parts or service information.
What is the difference between the main and pilot jet on a Yamaha G23?
The pilot circuit controls idle and very low-throttle fueling. The main jet becomes dominant as airflow, throttle opening and engine load increase.
Jet sizes can change with engine, carburetor revision, model year and altitude. This page applies to the carbureted gasoline version. Do not drill jets or assume a jet from another model is equivalent. Confirm the engine, carburetor ID and existing jet markings for your exact Yamaha G23. For manufacturer documentation, visit the official manufacturer website.