jimkron

Is there an earlier version of the FG 90? I'm not sure. You might be confusing the FG 90 with the FG 84. ( I have both). The FG 90 is nothing but a bored out FG 84 PLUS some mods for better fuel distribution. These mods were developed by Ray English and implemented into the FG 90. AFTER the FG 90 came out, Ray (and others) discovered that the timing could be improved by moving the magnet on the hub. Ray has worked on all my Saitos and I'm very pleased with the results including the Hub mod. A fellow flyer at my club recently bought a FG 90 and decided not to get the timing mod. Engine performed just fine. My suggestion would be to break-in the engine on the ground. Let it run rich for 2-3 tanks at 3000 rpm. At this point don't worry about running smoothly. Should be blubbery...is that a word? I would clean plugs or even replace depending on how rich you were running. For tuning, a perfect ground RPM would be between 5800 and 6200 with a smooth and quick transition to 1200rpm at low throttle. 15:1 Klotz oil mix is the best and will keep engine happy. If you have telemetry, keep those RPMs around 6600+- after unloading in the air. RPMs above 7000 risk destruction.

An earlier post suggested temps should be less than 165c (329f) and cylinders within 5c (41f) of each other. This can be a bit misleading. This engine should be no where near 165c or 329f...even during break-in. I prefer high temps around 250f at full throttle. As you come off throttle while flying, temps should slowly reduce from their highs. Also, I would like to see engine temps within 15f+- of each other on the ground.

Hope this helps,
jim