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Written by Don Apostolico
As featured on page 35 in the February 2012 issue.
Read an abridged summary and highlights from the article.

SOME FIND OUT the hard way when buying a used gas engine that a good deal sometimes turns out to be the worst deal, and the cheapest sometimes turns out to be the most expensive.

Avoid purchasing troublesome used engines by first determining if the current owner misused the engine. One thing is for sure: a problematic vibrating or erratic running engine is no fun, is a disappointing experience, and is often the most expensive way to go.

Below are excerpts from the February 2012 article, How to Buy A Used Gas Engine.

A tachometer, along with the decades-old pinch test, is used to set the high- and low-speed needles. Set a 100 rpm rise for gas while the fuel line is pinched.

Properly vertical and horizontal balance of a propeller and spinner is important. Use a high-quality balancer to eliminate vibration damage to your airplane and engine.

To track a propeller, rotate it from 12 to 6 o’clock. The propeller tip should be the same distance from the reference point on both tips.

Correct baffling is essential to keep engines from overheating. Proper baffling can drop cylinder temperatures by more than 100°.

Modelers can bend this little fulcrum while working on the carburetor. This unit controls the internal pumping pressure and if bent, the carburetor will be out of tolerance.

The author uses a pop-off pressure gauge to check the internal calibration of the internal needle and spring pressure.

Fromeco’s TNC tachometer is used to measure, set, and adjust needle valve settings. Every modeler can be a “local expert” if he or she sets up an engine by the numbers.

Spark plugs are a diary of your engine’s operation. The white electrode plug has been run lean.

The tan electrode on this spark plug shows the needles are correctly set.

The black electrode on this spark plug denotes an engine that has been run rich.

Read the entire text on page 35 in the February 2012 issue of Model Aviation.

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