Homemade Moped

Mopeds are often illegally tuned for higher speeds, powers or engine displacements than allowed. For this to be legal, such vehicles should be re-registered as motorcycles, and their driver's license requirements, insurance costs and minimum driver age would be higher. A tuned vehicle, not designed for higher speeds, is not as safe as a purpose-designed motorcycle. A survey of Finnish high school students found that 80% and 70% of their mopeds were tuned, for vocational and gymnasium students, respectively. Only 10% of trade school students had a moped to conformed to legistlation. The average maximum speed was 72 km/h, far higher than the legally allowable 45 km/h.
Emissions
Mopeds can achieve fuel economy of over 100 mpg-US (2.4 L/100 km; 120 mpg-imp). The emissions of mopeds have been the subject of multiple studies. Studies have found that two-stroke 50 cc mopeds, with and without catalytic converters, emit ten to thirty times the hydrocarbons and particulate emissions of the outdated Euro 3 automobile standards. In the same study, four-stroke mopeds, with and without catalytic converters, emitted three to eight times the hydrocarbons and particulate emissions of the Euro 3 automobile standards. Approximate parity with automobiles was achieved with NOx emissions in these studies. Emissions performance was tested on a g/km basis and was unaffected by fuel economy. Currently in the United States, the EPA allows motorcycles, scooters, and mopeds with engine displacements less than 280cc to emit ten times the NOx and six times the CO than the median Tier II bin 5 automobile regulations. An additional air quality challenge can also arise from the use of moped and scooter transportation over automobiles, as a higher density of motorized vehicles can be supported by existing transportation infrastructure.