||I had bought this motor for my custom 500 build in I believe January earlier this year. I had never heard of Viper R/C motors and from the looks of the description, it looked pretty robust. - It was worth a shot. I've paired this motor with a Castle Creations Talon 90A and am using a Turnigy 18.5V, 4000mAh, 35C battery. Initial tests with the motor were causing both my motor and ESC to run extremely hot. Even during minor hover tests. Then I started reading reviews about this exact issue with these motors. However, I was not too keen on giving up that easily. With some tweaking to the PWM settings, RPM gov'd, throttle curve, pitch curve, and placement of my ESC, I was able to get my heli flying the way I like and its power system running the way I like. I'm getting close to 7 minutes of Sport flying. My settings are as follows:
PWM: 8* (Found this setting to run around 23* cooler than 12* PWM)
Set RPM: 2603 with a 15T (Done with Castle Link)
TC: 0, 60, 70, 70, 70 Norm; 100, 95, 90, 95, 100 STM1
PC: 39, 50, 61, 73, 87 (-2, 0, +2, +6, +11*) Norm; 0, 25, 50, 75, 100 (-14 thru +14*) STM1
I am still playing around with my PC's to find my sweet spot, but so far, where it is now seems to be pretty close. It'll get better!
Now your settings may vary as the air density here in CO will be slightly different than your location.
Overall, I love this motor. TONS of power.