By changing the settings on either a 50 cc or 100 cc carburetor for a leaner air-fuel mixture, the newly developed 2-cycle engine exhaust gas purification system reduces the amount of pollutants generated during the combustion process. The unit also contains a new kind of oxidizing catalyst unit (the catalyzer) fitted inside the muffler. Compared with conventional 2-cycle engines, these modifications reduce the amount of pollutant gases in the exhaust by a substantial degree - reducing carbon monoxide (CO) and nitrogen oxide (NOx) emissions both by half, and hydrocarbon (HC) emissions by more than two-thirds. (Values are for Honda-conducted tests on Honda products). This system complies with both sets of impending Japanese motorcycle exhaust emission regulations - those for Class I motorcycles (less than 50 cc), which will come into force in October 1998, as well as those for Class II motorcycles (50 cc ~ 125 cc), which become law in October 1999.

The catalyzer unit has been developed exclusively for use with 2-cycle engines. Made out of stainless steel with a platinum and rhodium coating, the unit is highly effective at purifying the exhaust gas stream, as well as being highly durable and compact.

The new environment-friendly 2-cycle engine exhaust gas purification system will be fitted first to the new Lead series due to be launched in the near future.

Catalyzer unit (cutaway model)

Internal muffler construction

Exhaust gas type	Values for 2-cycle engines	Planned specifications for the new 2-cycle engines (same for 50 cc and 100 cc)
CO concentration when idling (%)	4.5	3.5
HC concentration when idling (ppm)	7,800	4,500
Weight of gases emitted - CO (g/km)	14.4 (8)	6.45
Weight of gases emitted - HC (g/km)	5.26 (3)	2.40
Weight of gases emitted - NOx (g/km)	0.14 (0.1)	0.05

(Figures in parentheses are average regulation values)

Regulations for new Class I motorcycles come into force from October 1998.
Regulations for new Class II motorcycles come into force from October 1999.