One of the great features that make giant-scale airplanes so popular is the bulletproof, user-friendly nature of the Walbro carburetors that most gas engines are equipped with. Once a gas engine is properly adjusted, its carburetor won’t usually need to be tweaked again for most of, if not all of the flying season. As an example, my old Hangar 9 quarter-scale Piper J-3 Cub PNP is powered by a Zenoah G-20 gas engine, and in its many years of operation, I have adjusted the high- or low-end needle valves only a couple times. However, to maintain optimum engine operation, you should do some basic engine maintenance and cleaning. Here is a video I made showing the last time I cleaned and rebuilt the Walbro caruretor.