I cant cite the source for this first item because I read it in a magazine article. The article went into detail on mag and engine problems and how to diagnose them.
The article said that normal mag checks should not be done at a high rpm because, at higher rpm numbers, some kinds of problems are masked. If I remember correctly, they recommended doing the mag check at 1500 rpm. This is the number I used. However, the O-200 Operators Manual says warmup should be done at 1200 rpm and, Increase engine speed to 1700 RPM only long enough to perform the following checks: then it lists the mag check procedure. In the Overhaul Manual for the C-75, C-85, C-90 and O-200, Section VII OPERATING INSTRUCTIONS (page 40), it instructs the operator to open the throttle gradually until the engine is running at approximately 1200 R.P.M. Do not exceed this speed until oil temperature has reached 75° F. In the next section, GOUND TEST, it says to do the mag check but nowhere does it say to increase the rpm above 1200 rpm. http://www.pj260.com/Continental/O-200%20Manual.pdf Ed
