The objective of this study is to investigate the effect of bioethanol-gasoline blends on the exhaust emissions and engine combustion of a four-stroke motorcycle. Ethanol is known as an alternative fuel for spark-ignition engines and is suitable for making blends with gasoline, increasing the oxygen content and decreasing emission of incomplete combustion products. An experimental investigation was performed on a Euro 3 large-size motorcycle fuelled with commercial gasoline and bioethanol/gasoline blends (range of bioethanol 5% v to 30% v). Regulated and unregulated emissions and fuel consumption were quantified over the execution of chassis-dynamometer tests. The combustion analysis, realized by acquiring the pressure cycle inside the cylinder, highlights the auto adjustment of the engine control unit and guarantees use within the same parameters of several tested fuels, with the except of fuel injection time, which increases with increasing ethanol percentage. A significant reduction in carbon monoxide and particle number is associated with the ethanol content of the fuel. Volatile organic compounds, mainly alkanes and aromatics, are not substantially influenced by the bioethanol content of the fuel. The contribution of carcinogenic benzene ranges between 2 and 5%.