I would sell the car complete.. but not separate the engines...
the reason for the upgrade to the 15 was i wanted more power.. but then i went back to the 12's because its easier to tune when you drift with them.
yes they are pull start. and i have only used 10% nitro not 15% like you are meant to when racing. I used the lower percentage mix because of the low speed drifting at high revs.
how much are you willing to pay for the complete car setup???