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.