THE MAIN JET
It’s one of the most important elements of the carburetor’s adjustment, because it calibrates the fuel delivered by the main system. To begin you have to try some jets, and it is good to start with a bigger jet to prevent the engine damage with a too poor fuel mixture that would lead to a seizure or piston drilling. Proceed by trial and error: after having driven a straight at full throttle at the highest rpm check the spark plug color (see spark plug color table). When you find the proper jet it is important to increase the size of a few points as a precaution because a mixture weakening could have passed caused by temperature lowering or by an increase of the environmental pressure.
SPARK PLUG COLOR INDICATIONS
It’s one of the most important elements of the carburetor’s adjustment, because it calibrates the fuel delivered by the main system. To begin you have to try some jets, and it is good to start with a bigger jet to prevent the engine damage with a too poor fuel mixture that would lead to a seizure or piston drilling. Proceed by trial and error: after having driven a straight at full throttle at the highest rpm check the spark plug color (see spark plug color table). When you find the proper jet it is important to increase the size of a few points as a precaution because a mixture weakening could have passed caused by temperature lowering or by an increase of the environmental pressure.
SPARK PLUG COLOR INDICATIONS
- NORMAL: From dark brown to light brown with dry electrode
- OVERHEATED: Light grey or white ⇒ Poor mixture
- WET: Wet or sooty ⇒ Reach mixture
![[Classic] Benelli 491 1997](/data/resource_icons/0/763.jpg?1668655751){kind=icon}
