Yep. The scooter might output less CO2, but due to the primitive nature of the 2-stroke engine, it's basically chucking a rich aerosol of unburned fuel and lubr

Yep. The scooter might output less CO2, but due to the primitive nature of the 2-stroke engine, it's basically chucking a rich aerosol of unburned fuel and lubricating oil out the exhaust. The X5, by comparison, has a catalytic converter to get rid of carbon monoxide, nitrogen oxides and unburned fuel, plus a particulate filter to get rid of soot; it will also have secondary emission control systems to stop fuel vapours escaping from the fuel tank and crankcase. 2-strokes have remarkable power-to-weight ratios and are pleasingly mechanically simple, but goodness me they're dirty.