This story about Saito FG 60R3 radial engine. All the times engine shows significant vibration level, from idle speed to the mid RPM. Vibration amplitude sometimes is so high, that bench stand is shaking. I'm absolutely sure, that something is wring with this engine, so I start a long time wasting test runs, and provide it dozens of times. I change basically, everything, what was possible, ignition type ( from spark to glow, fuel, from gaz mix to glow methanol based fuel, I even convert the engine to the glow fuel, by borrowing the glow fuel carb from Saito FA 180). In general, there nothing was changed in engine's behavior. Vibrations level becomes lower only, if engine was operated on glow ignition ( with the help of OS G5 type glow plugs). It similar perform on glow fuel and on gas fuel on glow ignition Spark ignition adds some extreme in engine's bench stand movement.
Becomes more and more clear, that this problems are appears due to uneven \ incorrect cylinder #2 and #3 firing, probably, it was a design flaw from the beginning. CH Ignition Company has developed and producing corrected prop flanges, were magnets are shifted to achieve exact time firing in #2 and #3 cylinders. Sounds very logically. New cure for FG60 was ordered, received, and of course, immediately installed. This video is about what and how it happens later.
Thank you for watching and have a nice day !