Snow Mobile--Ski-Doo Bombardier 1975, coil not getting power, what do I do?

hi, I have a ski-doo bombardier snowmobile,the year is 1975, it runs but only on one coil, the right coil is not running, i tried changing coils but that did nothing, it doesent have enough power to even push the sled, but when i lift up the back, the track spins. I tried 3 coils already. non work, the coils are fine, ther brandnew but i dont know why its not running, help me please!