Tuesday, 8 September 2009

Jetex carb air mixture screw


The setting for the Jetex air mixture screw is different to that of a Dell'orto, so don't blindly follow advice for the wrong carb. For a Dellorto SH carb we are told to start off about 1 ½ turns and go from there. For a Jetex however, there's a label on the side that clearly states we shouldn't be going more than ¾ turns out.

To set the mixture properly, first warm up your engine. Then set the throttle idle screw (no. 26 in the diagram above) so that it holds the throttle open with the engine slightly fast. Now we need to set the mixture screw (no. 13) so that the engine is smooth and regular. Turning the screw in will make the mixture leaner, and out will richen it. When you have the smoothest tickover try opening the throttle. If the engine splutters or stops then a little more adjustment, probably to make it richer, is needed to eliminate this.

You'll probably end up somewhere between ½ and ¾ turns out.

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