Yes, think in terms of how the crank/rod/piston motion is. On the down stroke it's tugged down but also the rod is being slung back toward the intake and on th up stroke it's being thrown up, but also a bit toward the exhaust. That's why you see the egg shaped bores on motors with more hours. To help combat that issue, the common solution is a longer for to create less angle so there is less fore & aft thrust.