Hey guys, I'm trying to learn more about brushless motors and how the batteries voltage affect them and max RPM's, current draw etc...and was hoping someone can share some experience or knowledge on the specs of this motor. I have used 2S on it and maxed the gearing out on 2S, being that a bigger pinion won't fit (2WD ECX Torment- 23T Pinion -Stock 87T Spur). I'm sure I could run the risk of meshing properly and really squeeze some more teeth in there but...why risk it? LOL. My question is, being that this motor is rated at 5200KV, even tho the ad says it can handles 2-4S, would the motor be at risk of KABOOM because of such high RPMS? Being a 3650 sized motor, from what I've read the max RPM "safely" on these is approximately 50,000Rpms, 3S would give it just above 60,000 Rpms. Has anyone had experience with this, and if so could you share some knowledge in how to read the specs provided? I maxed this thing out at 79km/h so far...few more runs to make sure before we go 3S IF we even can or SHOULD. I have had 4 full throttle passes on this back to back with 2S and she only gets to about 125 deg F.
Cheers and thanks in advance,

Name: 3650 RC
Motor Body
Length: 50 mm Motor
Diameter: 36 mm
Shaft Length: 15 mm
Shaft Diameter: 3 mm
Rotor Poles: 4 Operating
Voltage: 2-4S Motor KV: 5200KV
No-load Current (11.1 V): 2.0 A/2.8 A/3.7 A
Maximum DC Current: 70A / 75A / 95A
Maximum Continuous Power: 900W

I would go no more than 2S for 5400KV, if you want to run without any restrictions to battery capacity.

Yes that motor can technically handle up to 4S but that would be limited to very short bursts like speed runs, and then waiting for the motor to cool down.

More info here on the importance of investing in a temp gun:

• What gearing for upgraded electronics?

I have a temp gun, and for the geaing I have it at it only gets to 125 deg F after 3-4 good long pulls full pop and if it's cool outside I can run it 6 or 7 good pulls flat out. My question is that with 3S would the RPM's be too much for that motor full speed on 3S? I think something like North of 60 or 70, 000 RPMs is what it mathed out at.

Going off this motor chart here from HobbyWing, I would stay with 2S:


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It'll be able to hit around 65k RPM unloaded, but when actually pushing the vehicle I doubt it'll exceed 50k. 3S is the upper limit that I'd consider trying with that motor, but it's not without risk.

4600 is what I consider the upper limit for kv on 3s. Certainly not 5200. That to me is a 2s motor.

I run a 4.5T on 3S for Velodrome speed runs (approx 7000KV). It's doable.

OK guys, thank you for the input. I appreciate the insight and information. I have decided to stay with 2S as long as possible. I've ordered a 72 tooth spur gear and some gasket material to start trying to DIY my own slipper clutch pad material, I don't see the issue as I am only speed running this thing and it won't see jumps with this set up.

HOWEVER! It will get a final send on 3S for one pass once I have a replacement motor and ESC and I'm done playing with the gearing. Just did some minor dremmeling to fit a 25T pinion in the 2WD ECX Torment with the stock 87T spur gear. Should hit 84-86km/h, 23T grabbed 79km/h.

I will expect failure and be prepared for an explosion lol. I don't see the battery being an issue, but would the failure point be the motor physically letting go or letting the smoke out?

Update on this set up, we maxed out at 82km/h due to tires, belted tires ordered. Still only on 2S, temps reched 140degF after 4 passes.

Installed a 35T Pinion and 72T Spur gear, 82km/h because of tires losing contact after balooning.

You might need to move to foam tyres when you go even faster. Even the belted tyres can come off the rims.