Yes there is another thing to watch out for: Most .049 engines will run backwards just as well as they will run forwards. I used to keep a rag handy to throw into the prop so that I could quickly stop an engine that was running backwards. If I used the needle valve to stop the engine, it would take too long to relocate the "sweet spot" setting where the engine would start easily. Also, remember, it is very easy to flood an .049 engine, and when you do, you must wait a while to let it dry out. Howver, a drop of two of fuel in the exhaust port will help the engine start and run long enough to get a steady flow of fuel going through the intake.

Another thought: Once you have the engine started, you need to adjust the fuel flow with the needle valve. Clockwise makes it leaner, CCW makes it richer. The engine will prefer to start rich, but it will need to be adjusted leaner to run efficiently. The adjustment can be done by ear, closing the valve causes a rising howl as the fuel mixture gets leaner. Too lean, and the engine will stop. If you open the valve, the engine will begin to splutter, so close it from that point until it stops spluttering and begins to howl. Remember that when you are flying, the engine will be running leaner than on the ground, so don't make the engine reach maximum howl on the ground.