The Free-Piston Engine (FPE) offers variable compression ratio control and crankshaft-less operation, yielding a simplified, compact design with reduced friction, lower maintenance, and enhanced fuel efficiency over conventional Internal Combustion Engines (ICEs). However, widespread adoption is hindered by challenges in engine startup and achieving stable operation. This study introduces a dual two-stroke, spark-ignition gasoline FPE with a novel starting mechanism that excludes an integrated linear motor. Simulations indicated successful ignition is achievable at a 0.7 m/s piston velocity, a 3:1 initial compression ratio, a 2 mg fuel injection mass, and a 2–5 ms combustion duration, generating cylinder pressures of approximately 8 bar. The proposed mechanical resonance-based starting method was experimentally validated. The system attained the target 3:1 compression ratio and a piston velocity of about 0.7 m/s with a 400 N motor pull force applied over 1.4 s. During startup, cylinder pressure reached about 4 bar before the ignition event produced a peak pressure of 13 bar. The engine then transitioned to stable, multi-cycle operation, achieving consistent peak cylinder pressures of 12 bar.