A clod even though has 2 motors still puts most of the load on the rear motor, which we use motors designed for 1/10th scale light trucks, buggies,
So it will always tend to run warm.
Haven said that 140-150 is Plenty safe in a clod set-up.
The surface you run on, the amount of time you stay in throttle, how much brake you use, the tire weight,(rotating) truck weight and gearing make a difference, the outside air temp makes alot of difference so you are in a safe "ball park".
As today you may have been in grass, and doing long runs,
tomorrow you may be on concrete doing short runs, today may have been 60 degrees out, tommorrow may be 95 outside.
The ESC, and Battery temps usally tell you how hard you are maxxing the system before motor temp alone does..
Now some motors run warmer than others,
Some are not capable of pulling enough amps to heat your ESC or Battery,
and there are some motors that pull so hard, it can heat the battery beyond safe temps quickly unless you regear.
LOTS of things that lead up to a safe level, of temps, and loads across the board.
...and use some thermal grease between the motor and sink for maximum heat xfer ability. 
