Final answer:
The problem with high emissions in a two-stroke engine arises due to the simultaneous opening of intake and exhaust ports, which causes some of the fuel-air mixture to escape, leading to higher emissions compared to the efficiency of a four-stroke engine that follows the Otto cycle.
Step-by-step explanation:
One of the problems with high emissions in a two-stroke engine is that the design of the engine allows for some of the fuel and air mixture to escape during the intake and exhaust strokes. This occurs because there is an overlap in a two-stroke engine where the intake and exhaust ports are open at the same time. Unlike the four-stroke engine, which follows the Otto cycle, a two-stroke engine does not have a dedicated exhaust stroke to expel all the burnt gases before the new fuel-air mixture is introduced. Therefore, some unburnt fuel escapes, leading to higher emissions of hydrocarbons. Furthermore, two-stroke engines may not burn the fuel as efficiently as four-stroke engines, potentially resulting in higher emissions of carbon monoxide and nitrogen oxides, which can contribute to smog and harm the environment.