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Adjusting Air screw?

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I've heard that it is sometimes necessary to adjust the airscrew on the carb according to the weather/ temp. Is there anyone who would care to give some basic guidelines. IE overcast and cold turn it 1/4 turn in. Thanks.

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Our 450 always seems to be happy with it set at 1 3/4 turns out. When the outside temp gets colder we would have to richen it up to about 2 turns. The weather does not seem to affect the motor as much as it does on a 2-stroke, it had to be probably below 40 degrees before having to change the fuel screw, the rest of the time it was fine at 1 3/4 turns. I guess if you are in South Africa your jetting may be very different than ours but as a rule cold weather needs more fuel and hot weather less fuel. Humidity gets a little more tricky but once you get jetted your fuel screw should be close in one spot.

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Thanks mx206. If I understand you correctly, turning it out makes the mixture richer (more fuel than air?) and turning it in makes it leaner. If its cold you should turn it out, if necessary. :thumbsup:

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4-strokes have fuel mixture screws

2-strokes have air mixture screws

Turning the fuel mixture screw out on a 4-stroke adds more fuel, hence richer

Turning the air mixture screw in on a 2-stroke decreases the air, hence richer

So your original comment, where you say "air" screw and turning in for richer is correct...if you have a 2-stroke

Mxracer206's comments are correct as he is describing the fuel screw on the RM-Z450. Follow his guidelines.

Hope that helps clear up your confusion!

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