That sounds exactly like mine when timing was off. Keep in mind that these trucks set timing at before top dead center. To quickly get tdc, stick a kebab skewer in cylinder 1, turn the crank until the skewer is at the peak of the cylinder, and then tear down everything to check the timing marks. You can turn the crank counterclockwise maybe 1/16th of a turn to line up and lock the back of the intake and exhaust cams of each side. The crankshaft chuck should be pointed at the 6 o'clock position. Then line up the chains.