Something I've wondered is why the single cylinder two-stroke gas engines that we use for our planes don't idle at a slower speed. Why won't they idle at say 800 rpm? Is the reason that there isn't enough mass turning to overcome the compression? In my experience heavier props tend to make a gas engine idle better and slower, but I am not sure if the flywheel effect is the main reason why they won't idle lower. I am not having any particular problems with my planes--my gas engines idle around 1700 (sometimes 1600, sometimes 1800 depending upon the day), which is fine for me, just curious. Thoughts?

-Ed B.

You're correct about the flywheel effect.

You should not start an engine like this without some kind of load on it--magneto--prop--clutch assembly--chain etc.. But if you were to take the prop off and start it--you'd be hard pressed to get an idle under 3000RPM. Without a flywheel to keep the inertia and momentum going--it would have to idle very fast to overcome the compression.