I bought a few T-Maxx trucks from a guy on craigslist to have something to tinker with before its actually warm enough to drive out there. The first truck I am working on is a 2.5 that ran well but I like to break them all the way down and clean them really good. To me its the only real way to find all the flaws of a used truck. So when I took the motor apart the top of the piston had a lot of carbon on it. I tried a couple of methods to remove it without using anything that would damage the piston with no luck. Then a simple search from the google machine mentioned toothpaste and a toothbrush. In about 30 seconds that thing looked almost new compared to the 20 minutes I tried other cleaners and elbow grease. I cleaned off the toothpaste and oiled it back up and it fired right up. I wish I would have taken a before picture!