In this research, the bio-hydrogen and hydrogen-rich gas was added to 4-stroke carburetor motorcycle engine. The hydrogen and nitrogen were mixed as hydrogen-rich gas. The effect of hydrogen-rich and biohydrogen gas on the performance and exhaust emissions was evaluated. The effect of intake-gas positions, different hydrogen-rich gas volume ratio and flow rate were also investigated. The results of this test showed that: hydrogen-rich and bio-hydrogen gas could make engine with higher performance. Hydrogen adding rate reduced, the CO and HC engine exhaust emissions were decreased. Hydrogen-rich rate gas increased, the NOX and CO2 engine exhaust emissions were decreased. With no hydrogen gas adding, the engine exhaust emissions were better.