Replacing Main Burners
1)Your Weber Gas Barbecue must be OFF and cool.
2)Turn gas OFF at source.
3)To remove control panel: take off the burner control knobs. Remove the screws holding the control panel in place. Lift off the control panel.
4)Unhook the manifold bracket(1) and unscrew the two wing nuts(2) that hold the manifold to the cooking box. Pull the manifold and valve assembly out of the burners and carefully set it down.
(1) 
(2)
5)Slide the burner assembly out from under the guide screw and washer(1) in the corners of the cooking box.
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6)Lift and twist the burner assembly slightly, to separate the crossover tube(1) from the burners. Remove the burners from the cooking box.
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7) To reinstall the burners, reverse 3) through 7).
CAUTION: The burner openings(1) must be positioned properly over the valve orifices(2). Check proper assembly before fastening manifold in
place.
(2)
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WARNING: After reinstalling the gas lines, they should be leak checked with a soap and water solution before using the barbecue. (See Step: “Check for gas leaks.”)