Two-stroke engines have three important advantages
over four-stroke engines:
- Two-stroke engines do not have valves, which
simplifies their construction and lowers their weight.
- Two-stroke engines fire once every revolution,
while four-stroke engines fire once every other revolution. This gives
two-stroke engines a significant power boost.
- Two-stroke engines can work in any orientation,
which can be important in something like a chainsaw. A standard
four-stroke engine may have problems with oil flow unless it is upright,
and solving this problem can add complexity to the engine.
These advantages make two-stroke engines lighter, simpler and less
expensive to manufacture. Two-stroke engines also have the potential to pack
about twice the power into the same space because there are twice as many power
strokes per revolution. The combination of lightweight and twice the power
gives two-stroke engines a great power-to-weight ratio compared to many
four-stroke engine designs.