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The Goodman B4089343 is a genuine OEM #43 gas burner orifice engineered for GMTH090-5B gas furnaces. The orifice meters the precise flow of natural gas into each burner, ensuring a clean, efficient flame and proper heat output. A worn, clogged, or incorrectly drilled orifice causes lazy yellow flames, sooting, delayed ignition, and reduced efficiency — replacing it restores factory combustion performance.
Genuine Goodman orifices are drilled and gauged to exact factory tolerances, so gas flow matches the furnace's rated BTU input. Aftermarket orifices often vary in bore diameter, which can throw off the air-fuel mixture and trip flame-sense or limit faults. For a safety-critical gas component, OEM is the recommended choice.
Moderate — requires shutting off gas, removing the burner assembly, and swapping the orifice with a nut driver. Gas connections should be leak-tested after install. If you are not comfortable working with gas, use a licensed HVAC technician.