read this thread with interest..low speed bucking that clears up at higher speeds is usually poor ignition to me....it is not just timing however....check dwell and condition of points as well an consider aftermarket electronic ignition. i suggest this not because original points condensor etc were of poor design, but because replacement parts are very shoddy (caps and rotors and condensors especially)....with electronic ignition the ills of the caps and rotors are less glaring.