brushless losi 8b

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Originally Posted by FG101C

Any ideas why my Medusa 36-70-1600kv motor got hot running 5s geared 14/45 in a Losi 8B. It ran awesome on 4s geared 16/45 and cool but wanted to try 5s to get a little more speed. I know the Losi 8ight diff ring and pinions are 40/13, and with that 45 tooth spur is why I think things get hot easy in this buggy.

I was running a NEU 1512/2.5/D/F (2050kv) on 4s but it got hot, over 175, on any gearing combo from 10/45 all they way to 16/45. All the typical things are ok, drivetrain is free, nothing hangs up. The only main difference I seem to notice is the majority of people on here don't run on a track in race conditions. Speed runs in a parking lot are not going to heat up the motor like running on a track will. I've only ever driven it on the track. There's no way I could run the 2650kv motor, would hit 200 in 5 minutes. Maybe my driving style needs work.

Any ideas or suggestion are greatly appreciated. Thanks.

Somethings going on with your setup. I mostly drive at the track and will run up to 15min non-stop race pace. I haven't had my motor over 150F (Medusa 60x2000 4S geared 13/46 or 14/46). I'd check a number of things:
1. All connections - after a run notice if any of the connections or wires are very hot or hotter than other wires. A bad connection will generate heat.
2. Air Flow - I have a number of large holes in the windshield and a few over both the ESC and motor. I also have the intake vents cut open as big as possible.
3. Diff setup - I'm wondering if you need a diff rebuild. If the oil is no longer doing it's job then the wheels will diff-out badly requiring a lot more throttle for a given amount of acceleration.
4. Gear mesh - sounds like you've changed pinions a lot, but maybe you're just running them too tight. There should be a little bit of free play btwn the spur and pinion at all times.
5. Bearings - A bad diff bearing will generate a lot of heat quick and bad hub bearings can to the same.

Check those and let us know what you find out.