Advanced Ignition troubleshoot

AeroVee Timing Adjustment

Yahoo AeroVee Group, message 2829:

Hello AeroVee Group-

There are a few AeroVee operators who continue to struggle with high cylinder head temperatures. We work closely with each individual to help determine the cause(s) of overheating for each specific installation, the timing of the secondary ignition is one possible cause which has recently been identified in factory testing.

While a mag check indicating little to no RPM drop has been our standard measure for timing of the secondary ignition, it may not identify an advanced timing condition which can contribute to high cylinder head temperatures. A simple flight test can be performed to see if your secondary ignition timing may be contributing to high cylinder head temperatures:

Under normal cruise power (2900 to 3400 rpm):

1. Turn off the secondary ignition and observe the cylinder head temperature.

2. Turn on the secondary ignition and turn off the Primary ignition. Observe the cylinder head temperature.

If the cylinder head temperature rises when operating on only the secondary ignition, the secondary ignition is advanced. Retard the secondary ignition by turning the magnet cap slightly clockwise, as viewed from the flywheel end of the engine.

3. Repeat the flight test.

It is important to remember that the AeroVee is an air-cooled engine and will not cool properly on the ground during extended run-ups, either with the cowling on or off. This test must only be performed in flight.

Blue Skies,

Kerry Fores
Sonex Aircraft, LLC
Tel (Info/Orders): 920.231.8297
Tel (Tech Line): 920.230.8324
Fax: 920.426.8333

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