"Here is a Y6 with hextronic 16g motors. I built it a year over a year ago and its still flying today. I have 8 inch props with 2s lipo on them but they work better with 6-7 inch props and 3s lipos.
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"I installed a battery and now I get s gps lock almost immediately on power up (8 to 13 sats in view in a minute). I also have no JP1 installed and only power the apm2 from the input rail using a ubec that outputs 5.03 volts. Anything much higher…"
"Check and make sure that you can read the prop size on each prop from above. When I built my y6 I put the bottom props upside down at first and could not take off. Just make sure the top of the prop is facing up. "
"If you press and hold the left menu button (+) it should bring up the radio setup menu. Scroll down to the bottom to Mode.
I had the same problem as you and I picked Mode 2 RUD THR ELE AIL to fix it. This works for me with er9x."