just my 10p's worth.... Rules...
for our Club500 all the motors are in a bag.... and on the day of the race, everyone picks a motor out of the bag... that way no one has time to tamper with the motors and if they do, they might not get the same motor at the next race...
that would solve the motor problem..!!
which your just left with the speed controller and Batteries/accumulator (lipo or Sub C nicad cells)
some speed controllers don't give the full wack of power to the motor...!!
some batteries are better than others...!!