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winter riding

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Does anyone know the trick to getting a yz250f started and running right in the winter, when the temp. is around 30 degrees. I know it needs to be jetted different, but I don't know what to jet it to.

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I usually adjust my fuel screw on hotter/colder than average days. When it's cold, the air is more dense (MORE air) so your normal setting may be lean. If you're lean, you want to richen the mixture so turn the fuel screw OUT (counter-clockwise) to richen it up. Generally no more than a 1/4 of a turn or so from your original settings.

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That's about all I needed to do as well. Open up the fuel screw some and it seemed to run great. The temp was around 20-25 degrees.

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Upsize your pilot jet by one and your main jet by one. Then adjust the fuel screw to clean it up. Changing both jets in addition to adjusting the fuel screw adjusts the jetting for the entire power range.

A lot depends on how close your jetting was to begin with.

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