Piston Hurricane tends to leave his body open more often than his head, and will sometimes duck your jabs, so you can keep pounding away at his body.
Piston's signature move is his Hurricane Rush. When he does this, he will jump away, then back toward the center. Then he will unleash a flurry of alternating high and low punches, although they're easy to block. Don't try dodging them. He finishes the series with an uppercut (telegraphed by squatting). The best way to counter the Hurricane Rush is to punch him—a well timed jab or body blow will work—just as he hops back into the center. He will be knocked down no matter how much health he still has.
If Piston manages to initiate his Hurricane Rush, you needn't block the entire exchange. Instead, begin throwing left jabs to his head, slightly spaced apart. With this timing, you will knock him out of every one of his punches without having to block.
If you knock down Piston Hurricane without having absorbed any damage, he won't get up! If Piston gets up, his first move when he gets up will be a crouching uppercut. Dodge it and continue pounding on him, or just land an immediate body blow, beating him to the punch.
Advanced: Piston Hurricane can be "stunned" early in the first round using right cross counters to his lead jab. When in the stunned state, he will stand defenseless so long as you continueously hit him. It's possible to knock him out in less than 30 seconds with this technique.
Piston is much more annoying this time around. He doesn't leave himself open a lot. Now he's more like Kid Quick but without an obvious pattern to bring him down.
He still does his Hurricane Rush, but it's more difficult to defend against. First, he varies his timing when he jumps back in, usually doing two hops and pausing between them. It's much more difficult to just whack him and send him to the canvas when he jumps in. You might end up getting a hit, but a little too late, then he'll just continue his rush. You can still take him down with one hit when he runs at you, it's just harder. If he stars the rush, you're in trouble. The biggest problem is that he will sustain it for much longer than before. Afterward, he will throw two relatively quick uppercuts (without ducking, Mr. Sandman style), followed by his normal uppercut. The easiest way to deal with his rush is to attack him with left jabs, with a slight pause between each. Once you get the right timing, you'll hit him repeatedly without taking any damage.
Piston does not have the right cross, so it is safe to lead with your left against him, but except early in the fight it will not be very helpful.
When you fill your KO meter, you get one "free punch" but then Piston will become very defensive. He'll jab occasionally. If you have more health, your best bet is to let him hit you (once). He'll follow up with body blow, which you can dodge and counter, refilling your KO meter, and letting you land another powerful right hook. If you don't have enough health to take damage, it's possible to land a body blow as he's trying to jab.