i have a o1 banshee with rz juggs but powervalve are not hooked up,i have pro circuit pipes front to back with kn filter with 300 main jet.i bought it two yrs ago and end of last summer left cylinder was back firering and head pipe was hot,so i took compression test 60 psi in left ,100 in right,.it still runs but i want to rebuild anyone have suggeastion want i should be looking for when i tear apart engine,teared boot ,crank bearings seals ecy. o yeah and my spark plug was grey like.