oliveDrab

So you're looking at a 4120/14 motor, 400 kV (rpms per volt), with a 60 amp ESC, using a 6S Lipo. Ok ... and the plane you want to put it on is a trainer with a 57-inch wingspan. Wow. Seems like a lot of motor for a 57 span trainer. Also, not sure a 6S battery would fit in it. You might have to use two 3S Lipos in series. If you are considering going electric, measure the inside of the fuselage where the battery goes to make sure your battery will fit in it.

Do you have a picture of your plane? Sounds like a high-wing trainer with a rubber-banded wing maybe.

Just for comparison ... On my 71" LT-40, I use a 4120/18 AXI motor, 515 kV, 75 amp ESC, using a 6S Lipo. And it's plenty of motor ... the plane will easily go straight up vertical. By the way, I don't use the BEC on my LT-40's. I provide a separate 6.0 volt 5 cell NimH battery to power the receiver and servos. But using the BEC on your ESC to power the receiver and servos will be fine ... as long as you don't use too big of a prop which can burn out your ESC/BEC, cause your airplane to be uncontrollable, and cause you to auger in (crash).

An example of how to smoke an ESC/BEC: I had a Rimfire .60 motor that called for a maximum 12x6 prop. Was using a 6S Lipo, a 75 amp Castle ESC, was using the BEC that came with the ESC. Tested the plane on the ground with an ampmeter to verify the motor/prop combo was not drawing more than 75 amps. It was ok so I flew it and it was ok ... not spectacular but ok. Then tried a more aggressive prop ... a 12x8. Flew the plane with the 12x8, gave it full throttle, then the engine quit and the plane no longer responded to control inputs on my transmitter. It lost it's brain and pancaked into some tall grass - undamaged mostly. A postmortem revealed a smoked wire coming out of the ESC - can't remember exactly which one.

Anyway - long story short - don't put a prop on your plane that's too aggressive for the motor! Use the manufacturers recommended prop(s) as a guideline and it's a good idea to test the motor/prop on the ground before flying it. See how many amps your motor/prop combination is drawing. And if it's drawing more amps than your ESC and/or motor can handle, then go with a less aggressive prop.