I just finish working on my T-rex V2. Everything seems to be set up properly. The heli hovers pretty good for a few seconds and then suddenly the mptor starts to bog down. I am using the stock motor (with 12T pinion) and ESC that came with the heli. I power it up with a 22C pack lipo. I even tried it on different lipo with same results. I also tried to put the same Align ESC (as the stock) also the same results. I couldn't find the problem. It seems I am out of options. Needing some help to figure it out.

you might either have too much pinion (try a 10t or 11t) or you might have too much pitch on the blades at a low rpm. since the pitch is easier to change try lowering the pitch curve to see if that helps.

You mention the max discharge rate of the battery, 22C, but you do not mention the capacity or the brand. Both are relevant pieces of info.

Sorry. I am using the 11.1v Align lipo with 2100mAh 22c.

What pitch are you running? If you follow Finless Bob's recommendation, a 5 point pitch curve in normal mode works out to be 40,45,50,75,100. This works perfect for me, about -2 degrees at 0 throttle and +11 degrees at 100% throttle.

If it is not a pitch problem and you have tried (2) good Lipo packs, I guess it could be a defective ESC or motor. Do you have a spare to try?

give that a shot, also unplug the motor and check your pitch, when i was learning to hover i used -2 and +8. Also, see if theres any binding in the head, give it full throttle and spin with your hand, see if its still easy to do.

All my set ups are base on Finless Bob's video. I also tried switching with my spare ESC still the same thing happens. Right now I am in the process of using the stock ESC and an Align motor which is the 3500kv with 12T pinion. I'll see what happens next.

Well after using different motor, ESC and pinions still the same results. The heli will hover for a few seconds and starts to bog down. Still needing help. Thank you.

what pitch?

you have not addressed that
Which pitch gauge are you using?

Maybe could be someting binding.Belt to tight ,Pinion to tight to the main gear.Everything should spin free .

If you are asking pitch values. I am using the once Finless Bobs recommends on his video. I am using the align pitcg gauge.

do you have someone local that can look at it?

No. I don't know anybody around here who flies heli. I've been doing these all by myself. Infact I got 3 other T-rex that I built but nothing like this happen to me before.

Go take a look at the [link=http://www.modelaircraft.org/clubsearch.aspx]AMA club search page[/link]. There are 16 clubs within 25 miles of zip code 60077. I bet that some of those clubs have some of the members who fly helis.