7XL Getting Hot
 

I have an ext. G-Maxx with a 9920 and 7XL. I was running at 20/66 gearing for months (on 14 cells) with no problem. The motor started to heat up, changed it to 18/66. After 10 or so runs, within less than 5 minutes, the 7XL temps exceed 160F, the controller at 125 and batts at 125. On 16 cells at 15/66 gearing, motor temps exceed 160F after only a few minutes.

There is no binding on the drivetrain and I have reprogrammed the controller. What should the timing be set at?

If you ran the same setup for a long time without any heat issues, something is definitely wrong. Binding would indeed be the first thought. Are you really sure the drivetrain is as smooth as ever? If yes, there might be a damage to the motor, such as windings getting their insulation ripped off from bouncing wires.
A bad motor bearing could also be the cause.

I ran the same setup, 7XL on 1 cells, 22/60 gearing, stock diffs, btw.

The factory settings of the BK controllers on timing is 15 degrees.

Yes, took the truck apart and checked it, no binding. Also removed the motor and it spins freely so the bearings are still good. Could it heat up if the spur gear is slipping excessively?

Could be. But then I would guess your stock spur would long have melted!?
Worth a try anyway.

I use the Robinson Racing Slipper setup w/ pads on each side of the gear. They rub against metal discs.

The slipper slipping can cause excess heat in the set up. I think the 20 66 sounds more touble free than the other lower gearing you tried. It is not holding a load on the motor to keep heat down.

It may be the slipper. I just got one and it says to check periodicaly for wear

Stupid Question- Where is the best place on a 7XL to use the temp gun? My heatsink and endbell are much cooler than the purple can.

I ussually try to get it from the can. It may be higher but it is what the windings are touching.

Definitely check the can's temperature. Another spot to check for temperature is on the pinion, which will give you an idea of the heat of the rotor (maybe 10-15 degrees less).

I have to run a fan on my 9920 as it gets so hot. I run a 7XL and just 14 cells. If a fan isn't used, it jolts alot at the mid to end of a run. 20/66 gearing.

I run fans on both the controller and motor. I ran it at 20/66 gearing on 14 cells over the weekend. The temps were batts-125 F, controller 120 F, motor 172 F.

I assume that my motor has gone bad.
What is the difference between the Wanderer XL and the 540C XL motors?

The 540c has built on heatsink.

Here is the latest. Geared 20/66 on 16 cells, motor gets hot at 1/2 pack (about 170F). After using 1/2 of my battery packs (GP3700's), motor runs in reverse until the fans can cool it down again. Controller is at 135F-140F, batts are cool.:007:

My drivetrain rolls very smoothly.

What do you mean the motor runs in reverse? That don't sound right.

When I hit the forward throttle after using the brakes, it goes backwards.

I don't know what to say on that one. That is a first I have heard. That would seem to be in the esc more than the motor. Have your tried another esc on that motor. Maybe the esc is running out of time and making the motor run hot.

Try to reprogram it.

I have re-programmed the controller. Why is my motor getting burning hot?

Check your motor bearings also. You can check it by hand spinning it. It should feel real smooth and should spin freely. Also check for any side to side movement of the shaft.

Another possibility, Any chance contaminates have gotten into the motor?

It's possible that the rotor is out of balance. I had this happen to my 380c 9t. It must have been whacked out of balance when the motor fell apart in bad crash. When my 380c 9t began to run hotter all of the sudden, I did some inspecting and found that the rotor was way out of balance. The epoxy was now on the wrong side of the rotor. Even when I rototed the epoxy holding aluminum plates 180 degress at the ends of the magnet, the rotor would still roll to one side when placed on a table. The shaft wasn't bent, but somehow the distribution of mass inside rotor must have changed. I don't know if this is the case with your motor, but it did make my 380c 9t run quite bit hotter. Be sure you rule out your esc first though.

Hey speedy did you make sure there was no metal screws in the table where you was testing.

I have decided to purchase another system. I run 14-16 cells, should I get the MGM Compro 160 amp or the BK Electronics 12020 Warrior Controller? I will probably stick w/ a 7 or 8XL motor.

Well after running my mgm. I would say get the mgm for up to 16 cells. It is a hard esc to program but is real smooth. for run time the 8xl would go longer.

What do you mean by smooth?

He means that the low-end throttle is less likely to cog with the MGM compared to the BK.

You might want to consider the Quark controller.

Yes I did. The rotor is so out of balance that you can even roll it on your fingers and it will still role to one side all the time. I'm going to add a whole bunch of epoxy to see if that solves it.

Edit: It turns out my rotor wasn't out of balance at all. The rediculous amount of epoxy that I put on one side of the rotor, did nothing at all and I began to wonder. I found out that the earth's magnetic field was pulling one side of the rotor down towards the ground, since the balance point slightly shifted depending on which direction the shaft was pointing (North or South). I guess rotor balance is not the issue after all for feigao motors.