The correct Yamaha Adventurer One 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.
Adventurer One • Main & pilot jet sizes
Adventurer One carburetor jet sizes at a glance
Main jet
Match the stamped main jet to the Yamaha/Mikuni carburetor ID.
Pilot jet
Match the stamped pilot or pilot jet to the 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 Adventurer One jet
Adventurer One 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.
Adventurer One jet specifications
Applies to: Carbureted gasoline version.
Engine: Yamaha gasoline; generation varies.
Carburetor: Yamaha/Mikuni carburetor; model-specific.
Main jet: Match the stamped main jet to the Yamaha/Mikuni carburetor ID.
Pilot jet: Match the stamped pilot or pilot jet to the carburetor ID.
Altitude: Use the manufacturer altitude chart where one is published.
Model-specific note
For the Yamaha Adventurer One, use the carburetor ID and model year rather than a generic Yamaha jet size.
Yamaha Adventurer One carburetor jet FAQ
What is the Yamaha Adventurer One main jet size?
Match the stamped main jet to the Yamaha/Mikuni carburetor ID. For the Yamaha Adventurer One, use the carburetor ID and model year rather than a generic Yamaha jet size.
What is the Yamaha Adventurer One pilot jet size?
Match the stamped pilot or pilot jet to the carburetor ID.
Does altitude change the Yamaha Adventurer One main jet?
Use the manufacturer altitude chart where one is published.
Can I install a larger jet in a Yamaha Adventurer One?
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 Adventurer One 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 Adventurer One?
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 Adventurer One. For manufacturer documentation, visit the official manufacturer website.