RE: G.P.Electric Sportster
the stock motor can run up to a 9.6 volt pack, so a 2 cell lipo is what you would use, this wont give you as much power since it will be between 7 and 8 volts, but the weight savings will help offset the slightly less full power, you will get a longer run time though overall, keep in mind the brushless is the key to getting to long run times, more than the pack. if you go the way of stock motor/2 cell lipo, then i would recommend about a 1500ma size lipo. it can be any lengh and hight to fit, but cant be more than 1.6 inches wide, look at the specs before you buy one. also with stock motor you will pull twice as much amps for the same power as a brushless, so i would recommend a speed contol of 20 amps just so you have room to use it on a bigger motor for future use, in reality my guess is you will pull about 12 or so amps at full throttle.