Causes and cures of this motor killer

Heat is a paramotor’s mortal enemy. Worst cases have the piston welding itself to the cylinder wall in the mother of all motor failures: a seizure. A close cousin is the piston burning a hole through it’s top. Molten material drops harmfully into the engine’s lower, and most expensive, workings.

There are a number of reasons why heat gets to this point. Here are most, starting with the most common.

1. Mixture is too lean: on carb adjustment. On floatbowl carbs this can be caused by having too small a jet.

2. Mixture too lean: Too much oil. At some point, oil replaces fuel and therefore the mixture goes up.

3. Mixture too lean: Air leak inside crankcase or cylinder. It can come from the cylinder, carburetor attachment, bearings, or exhaust.

4. Low RPM due to oversized or overpitched prop.

5. Blockage in fan (if equipped).

6. Piston ring sticking