When it first started doing it it was bone stock, tors and all... It ran fine for years; then one day it just started popping on the left side, so I figured it was a carb problem messed w/ carbs several times, and I mean several times, and it still didn't help... Then I decided if it was electrical, or an air leak I would fix it when I rebuilt the top-end and upgraded all my electrical, and put my v-force 3's in. Well, after all that it fixed it all right... Now it pops on the right side, and ten times worse... I can blip the throttle off idle and pop,pop, boom..... I figured maybe my timing was way off, so I set it to zero where the case split is, and still the same results.... Could a crank seal be causing it???????? Thanks in advance........