Engine Tech - Back to Basics Engine Tuning
For the benefit of our new fliers, we have put together some tips on how to properly setup and tune a gas or glow motor. A properly tuned engine will give many years of safe, happy flying and minimize the need for trashbags at the field.
One of the largest contributors to crashes is a poorly running, or not running, engine. A fresh, clean plug and clean fuel is a great place to start. After that, your carb must be adjusted properly to get a reliable transition from idle to full throttle.
An engine that runs badly on the ground,
will only get worse in the air!
Follow the manufacturer’s instructions for preliminary needle setting for both the low speed, and high speed needles. If you are running a glow engine, it will need to be fine tuned almost every time you fly because these engines are very sensitive to atmospheric conditions. Gasoline engines are not so sensitive.
Step 1 - Your low speed needle must be set so that when you go to full throttle, the engine neither lags, or sputters and cuts out. To accomplish this, use your normal starting procedure and after warmup, let the engine idle for 30 seconds followed by a quick movement to full throttle. If the engine dies, it is too rich on the low end and needs to have the needle adjusted for a leaner mixture. If the engine lags, then goes to full RPM, the low side is too lean and needs to be adjusted. Repeat this process until the engine transitions smoothly to high RPM.
Step 2 - Your high speed needle needs to be set so that when you are at full throttle, the engine has maximum power. This is accomplished by ear and you must be aware of what an engine sounds like that is too lean, or too rich. An engine that is too lean, will sound weak and flat and will overheat quickly, possibly causing a cylinder lock up. An engine that is too rich will burble and sputter. This condition will not harm the engine, but will not produce max power. While at full throttle and with the engine running on the rich side, slowly turn the high speed needle until the sputtering just goes away.
During engine break-in, most manufacturers advise you to run the engine a little on the rich side on the high speed needle to properly cool the engine while all the new parts work themselves in. If in doubt, ask any seasoned member for help. Good Luck!
