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The genuine Goodman B4089343 #43 Burner Orifice (gas spud) is a factory-original metering jet for the GMNT090-5B gas furnace. The orifice controls the exact volume of gas delivered into each in-shot burner, setting the furnace's BTU input and combustion quality. The #43 drill size is calibrated for the factory-specified gas type and manifold pressure, so replacing a damaged or wrong-sized orifice restores correct, safe firing.
Orifice sizing is not a place to improvise — an over- or under-drilled generic spud changes the air-fuel ratio, risking sooting, high CO, or nuisance lockouts. The OEM B4089343 is precision-machined to the exact #43 bore Goodman engineered for this furnace, ensuring correct BTU input and clean combustion.
Easy (2/5). Shut off gas and power, remove the burner, and thread the orifice out of the manifold with a properly sized wrench — do not over-tighten brass. Install the matching-size replacement, reassemble, and confirm a clean blue flame. About 15 minutes. Verify manifold pressure after service; if unsure, use a licensed technician.
Always shut off gas and electrical power before servicing.