The focus of this research work was understanding the effect of varying the secondary flow area in a single coaxial injector on flame stability in an experimental non-premixed flame burner. The reactants were methane and oxygen, mixed and ignited in a horizontally-mounted, rectangular combustion chamber using a retractable spark plug. Gaseous oxygen was the primary flow and gaseous methane was the secondary flow. Using optical windows on both sides of the chamber parallel to the axis of the flame, the product flame behavior and flame standoff distance was observed. Results will be presented on the stability of the non-premixed flame based upon equivalence ratio, reactant Reynolds numbers, and injector impingement angle.