A friend of mine gave me a hand-me-down EFlite Ultimate airframe. Since I already had most of the gear needed to make it fly again, less motor and gear box, I decide to get those items and fly this plane. I got the V2 gear box and Speed 370 brushless motor from Horizon. The motor came with two pinions -- a 10T and a 12T. Which should I use?

TIA for your help!

depends on the spur gear on your gearbox.... if you have the 66tooth "d" gear, then use the 10 tooth pinion. (makes a 6.6:1 geardown) if you have a 64 tooth "C" gear, then the 12 tooth. (makes a 5.3:1 geardown) if the spur gear on the gearbox is 62 teeth or smaller, I think you need a larger pinion than the 12.... If thats the case, I wuld reccomend buying a GWS or Eflite gearbox, in the D gearing.

It depends in the KV of the motor and the prop. If it's the 4100 then you should use a 12x6 prop and the 6.6:1 ratio, if it's the 5200 then you should use an 11x4.7 or 10x4.7 and the 6.6:1 ratio. I've got the 5200 and the 10x4.7 with the 6.6:1 is fine. The 11x4.7 prop works OK too but I'm worried about drawing too many amps.

I run a Feigao 6160kv brushless, and a TP 2s 1320, 5.33:1 gearbox, 10T pinion, and castle creations phoenix esc, Stock 12 x 6 prop, and it runs at around 11-13 amps with 22 - 24 ozs of thrust. More than enough power. Hovers at 1/4 throttle. Hope that helps a little.

I use rmgmag's setup on my Ultimate, and Tribute. Works fine, with a 2cell lipoly pack.