Yamaha WR250FM service manual Settings

SETTING

T U N

CAUTION:

•The carburetor is extremely sensitive to foreign matter (dirt, sand, water, etc.). During installation, do not allow foreign matter to get into the carburetor.

•Always handle the carburetor and its components carefully. Even slight scratches, bends or damage to carburetor parts may prevent the carburetor from functioning correctly. Carefully perform all servicing with the appropriate tools and without applying excessive force.

•When the engine is stopped or when riding at no load, do not open and close the throttle unnecessarily. Otherwise, too much fuel may be discharged, starting may become difficult or the engine may not run well.

•After installing the carburetor, check that the throttle operates correctly and opens and closes smoothly.

Atmospheric conditions			and	carburetor
settings
		Air
Air temp.	Humidity	pressure	Mixture		Setting
		(altitude)
High	High	Low (high)	Richer		Leaner
Low	Low	High (low)	Leaner		Richer

The air density (i.e., concentration of oxygen in the air) determines the richness or lean- ness of the air/fuel mixture. Therefore, refer to the above table for mixture settings.

That is:

•Higher temperature expands the air with its resultant reduced density.

•Higher humidity reduces the amount of oxy- gen in the air by so much of the water vapor in the same air.

•Lower atmospheric pressure (at a high alti- tude) reduces the density of the air.

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