Photo via motorbiker.orgvia: Greenlaunches
"Laying it down straight for you- the average motorcycle is 10 times more polluting per mile than a passenger car, light truck or SUV. Yes sir, that's the truth. Although bikes are twice as fuel-efficient as cars and emit a lot less C02; they account for 10 percent of passenger vehicles' smog-forming emissions. Bikes emit large amounts of nitrogen oxides, which along with hydrocarbons and carbon monoxide are measured by state and federal air quality regulators to determine whether vehicles meet emissions rules.
Catalytic converters and other emissions control devices would clean things up, but they're often too big, too heavy or too hot to install on motorcycles. So the next time you want to unnecessarily use your bike, think about the pollution it causes."