The majority of model engines have used, and continue to use, the two-stroke cycle principle to avoid needing valves in the combustion chamber, but a growing number of model engines use the four-stroke cycle design instead.
The majority of model engines have employed, and continue to utilize, the two-stroke cycle principle to circumvent the need for valves within the combustion chamber; however, a rising number of model engines are adopting the four-stroke cycle design instead.