1986-1989 Honda TRX250 FourTrax 250R Service Manual, Page 53Get this manual
FUEL SYSTEM This fina portion of the main circuit affects 1 2-to-full throttleThe mixture can be altered by chang ing the main jet
(1) NOZZLE (2) AIR JET
(4) MAIN JET
(3) MAIN JET HOLDER
CARBURETOR OPERATION
The operation of the carburetor is broken into throttle opening segments; each of the metering units is responsible for one segmentThere is always overlap from one segment to the next, so any change will always affect the next segment up or downBecause of th is, making carburetor adjustments for altitude or temperature should be done in methodica manner See page 3-12