Throttle up! Know your carburetor

Model Airplane News, Jul 2005 by Gierke, Dave

When your engine is mounted in an airplane, you can perform a simple "tip test" to determine whether the idle mixture is correct. With the tank half full and the engine idling, lower the model's tail; if the engine quits, the idle mixture is too lean. If the engine idle improves when the tail is lowered, the mixture is too rich and should be adjusted as previously described.

This test will work reliably only with air-bleed-type carburetors. Fuel-mixture carburetors (those with two needle valves) have too much fuel draw to be affected by tipping. Of course, the other good method for checking the idle mixture is to fly the model. If the engine idles well on taxi but quits when the tank is almost empty (during landing), the mixture should be richened slightly. Good luck with your first RC airplane!