I just found this information that will help in making a decision on which motor to get.
http://www.espritmodel.com/index.as...ROD&ProdID=8408

As you can see the HK4025 series all have a 28,000 RPM limit.

For the 1100 the voltage limit would be 28000/1100 = 25v or 7s.
For the 890 the voltage limit would be 28000/890 = 32v or 8s.
For the 740 the voltage limit would be 28000/740 = 38v or 10s
For the 630 the voltage limit would be 28000/630 = 44v or 12s

They might be good for a little over 28,000 but I would not go too high.

Also note that the 630Kv has the highest watt (power) limit so that motor on 12s would be the most powerful in the 4025 series.

... BTS

I have 8S now... thinking of going 12S so I can share batteries with my 500. Plus... 2 x good 6S packs are cheaper than an 8S brick.

trex 600 esp

Hey you guys,im running 8s with my set up with stock motor/14t..8s setup if perfect, just as long you keep your throttle curved around 75/80% v curved. i'll post a video next week reguarding this setup of mines.meanwhile i wish align makes a pinnon 13,12,&11 tooth pinnion gear in 6mm.. now that would be sweet!!!..

Im running 8s in my 600 and it has more power than my 700n its very fun to fly!!

MSH USA / Lynx Heli Innovations