I think I may have blown both my d3 21.5 motors. I ran what was I thought to be conservative settings. Well they were conservative at least when I ran them with a 5.4 ratio. The only change I made was change the ratio to 6:1. The car ran good for about 2 minutes before it came to a crawl. Checked temps with the temp gun but the motor's didn't measure hot. I've taken them out of the cars and noticed that the motors now have a lot of resistance inside them. The resistance doesn't feel like the magnet resistance you get when spinning the motor. Feels more like binding. I can't find anything obvious within the motor to say it looks like it is blown.
How exactly can you tell if a motor is blown?