The problem is that four-cycle engines won't fit on smaller models, and two-cycle engines have a longer lifespan, simpler construction, and lower production costs, making them popular with both manufacturers and consumers. So two-cycle models still make up more than 80 percent of all motorcycles and motor scooters on the road.
二行程則除了可以做小型車，壽命長、又跑得快，加上結構簡單，生產成本低、賣得便宜，業者、消費者都喜歡，一直無法「淘汰」，如今市面上的機車，二行程仍佔有百分之八十強。