Don't get the same kv motor in another brand. There wont be a significant change. Get the next step up in kv in any brand and gear it down. Your stampede will be faster than before, and since the more powerful motor isn't working as hard as the less powerful motor, it will run cooler.
If you can afford it, get a Castle Creations 4600kv 4 pole motor. It will run cooler and faster than your 4000kv.
If you cant afford that get a cheaper motor that is more than 4000kv, like the first generation Castle 4600kv 2 pole motor. (Yes, Castle makes two different 4600kv motors.) It is about $20-$25 cheaper than the 4 pole, and has been around a long time and is a good motor, just not as much torque (wheelie power) as the 4 pole. The 2 pole series are called CM36 motors and the 4 pole series are called 1406 motors. The Castle 4 pole motor will be amazing in your stampede. Save up for it.
The cheapest thing to do would be to try a fan. Any fan that says it will fit a 540 sized motor will fit a 540 sized motor. Look at the fans that are for sale online. You have to trim your engine shroud to get them to fit in your stampede, or mount it on the shroud with zip ties or something. Cut away the shroud right under the fan so that maximum air blows on the motor.
I suspect your next question is going to be for a link to the Castle motors and/or a price. Come on, don't you know how to do a search online?
Last edited by Rufus2010; 03-14-2011 at 11:02 PM.