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Old 02-20-2013, 09:22 AM   #3 (permalink)
Runs with scissors
Join Date: Jan 2013
Location: Illinois
Posts: 89

Spot - '05 Scion XA
90 day: 30.33 mpg (US)
Thanks: 7
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Partially plugged main jet causing lean condition

It appears the main jet is partially plugged. It's a pretty simple repair. Shut off or drain the fuel tank. Note if the fuel bowl has a step in the bottom and remember the orientation of it. Looking at the diagram, there is a screw at the very bottom - this is the main mixture adjustment. Gently screw it in, counting the turns required until it seats. Now remove the entire bowl by backing out the brass fitting directly under washer #44. Gently rock the bowl and remove it. Gently turn #20 (idle mix) screw in counting the turns until it seats. Now remove screw #20. Using a straw on a can of carb cleaner, spray through the opening screw #20 came out of. This will generally remove debris from the main jet port. Clean the bowl and main jet assembly with carb cleaner. Reinstall the bowl and the mixture screws. Refill the gas, and start it up running about 3/4 throttle. After it has warmed up, slowly screw the main jet inward until it begins to run rough. Back the main mixture screw out slowly until it runs smoothly and add 1/8 turn in the same direction. Return the throttle to idle speed and adjust the idle mixture screw by slowly turning it inward until the governor begins to surge and then slowly back it out until it smooths out again. Return the throttle to 3/4 and engage the auger. If it runs rough, back the main mixture screw out slowly until it runs smooth. Disengage the auger, and adjust the idle mix screw until it runs without surging. That should just about do it.

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