Motorcycle manufacturers face stricter emissions standards beginning in 2006 under new rules adopted by the U.S. Environmental Protection Agency.
 
   Environmentalists point fingers at sport-utility vehicles for generating more pollution than cars, but motorcycles are far worse than SUVs.
 
   A 1,800-cc Honda VTX motorcycle, for example, produces 0.48 grams of hydrocarbon emissions per mile, three times as much as a Ford Expedition with a V-8, according to the EPA. A typical motorcycle generates 18 to 24 times as much smog-causing pollution per mile as a typical passenger car, according to the EPA.

   No emission controls are currently specified for motorcycles.
 
   The EPA says the stricter rules will reduce hydrocarbon and oxides of nitrogen emissions from motorcycles by 60 percent when they are fully effective in 2010.
 
   Even then, motorcycles will still generate more pollution per mile than passenger cars and light trucks.
 
   The rules will apply to the more than 600,000 motorcycles and scooters sold annually for non-interstate highway use, from 50-cc mopeds to Harley-Davidson Electra Glides.

   The EPA estimates that the standards will add $75 to the $10,000 average cost of motorcycles. The agency expects manufacturers will use the same technology that automakers used to cut emissions, such as replacing carburetors with electronic fuel injection and adding catalytic converters to the exhaust system.

   "All the manufacturers know how to produce motorcycles that will meet these standards. It's just a question of how much it will cost," said Tom Austin, a consultant to the council on emissions regulations.