The utilization of methane–ammonia fuel blends in spark-ignition engines represents a viable strategy for reducing carbon emissions while capitalizing on the high hydrogen content and carbon-free nature of ammonia. Methane, characterized by its high octane number and low carbon content, offers improved thermal efficiency, higher compression ratios, and reduced pollutant emissions relative to conventional gasoline fuels. Ammonia, despite its advantageous energy density and zero carbon content, suffers from low flame speed and high ignition temperature, which pose challenges for stable combustion. Blending ammonia with methane addresses these limitations by enhancing ignition characteristics and flame stability while simultaneously reducing carbon-based emissions. This study examines the combustion and emission behavior of methane–ammonia blends in a single-cylinder, four-stroke engine under varying spark ignition configurations. Experiments were conducted across a range of ammonia energy fractions from 20% to 50%, with results compared to baseline pure methane combustion. Findings indicate that increasing ammonia content results in prolonged ignition delay and combustion duration due to ammonia's lower reactivity. Pure methane exhibited stable combustion and higher power output, whereas higher ammonia fractions led to increased cycle-to-cycle variability and reduced engine performance. However, the implementation of multiple spark plugs significantly improved combustion stability and engine performance by promoting faster heat release. Nitrogen oxides emissions increased with ammonia fraction, peaking at 30% and declining thereafter, while carbon-based emissions showed a marked reduction. High-speed natural flame luminosity imaging was employed to visualize flame front propagation across different blend conditions, providing insight into the influence of fuel composition and ignition strategy on combustion dynamics.