What kinda charger are you using? Alot have a motor run function that can be set to 2v. I like to breakin CO27's at 1v for 5min, it is really easy on the brushes, also be sure to oil the bushings before every run, after you breakin the motor, cut the comm (if you don't have a lathe ask around the track I am sure someone does) then your motor will be at peak performance. Also what brushes are you using? For that motor the F-Brushes sold by EA and Brood work Incredible. After 10-25 runs you will want to cut the comm again, some people will tell you to put in new brushes, but it really isn't necessary (only if they are burnt), the reason being is they are already broken in and conformed to the shape of the comm, if you have a serrattor you can do that but again it isn't a big deal.
Traxxas Slash 4x4, Team Checkpoint TC-1030 Charger and Power Supply, Team Checkpoint Lipo Balancer