I don’t know if this should be in the combo thread, but it has more to do with the mechanics of Street Fighter than the specific combo.
First of all, c.LK is +2f on hit. Legs comes out in 4 frames. This means that c.LK does not link into Legs.
Secondly, c.LK cannot be cancelled into specials. Not even Legs.
So, if c.LK can’t link into Legs and if c.LK can’t two-in-one into legs, how does c.LK XX legs work? This sounds weird, but it works because two properties in Street Fighter: The Rapid-Fire property and the mechanics of “tap repeatedly” special moves:
-The rapid-fire property is where certain jabs and shorts can cancel into each other. Jabs and shorts that can be canceled this way can chain into itself, allowing you to string together multiple jabs/shorts. This is the case with Chun-Li’s crouching LK. However, a jab/short that has been canceled into cannot cancel into a special/super… not that Chun-Li’s c.LK can be cancelled into specials/supers anyway.
-The way “tap repeatedly” special moves work, if you have five rapid taps of the appropriate buttons, the fifth tap will activate the special move. Each of the button taps can be of any strength, but simultaneously tapping multiple buttons count as one tap only. The strength of the fifth and final tap determines the strength of the special. If two buttons are used, this activates the EX version.
Now, back to Chun-Li’s crouching short. The rapid-fire property lets you combo multiple crouching shorts together. However, if one of the crouching shorts also happens to be the fifth button tap of your Legs, the previous crouching short will still be cancelled (a la rapid-fire), but the c.LK is replaced by LK Legs. If you used two kicks, you’ll get EX Legs.
So, essentially, you’re not linking c.LK into EX Legs nor are you cancelling c.LK into EX Legs. You are chaining c.LK into a phantom c.LK that never comes out because it’s replaced by an EX Legs. Sadly, you cannot get MK or HK Legs this way. This mechanic works the same way with Gen Mantis Hands (which is moot he can link into Hands anyway). Blanka and Honda don’t have rapid-fire jabs, so they can’t take advantage.
So, how is this information useful? Try this: Hit c.LK and just mindlessly mash on KKK.
As you mash on KKK, a second c.LK will come out (it is the only legal input when your first c.LK is in recovery), and eventually you’ll hit your fifth kick input and it will come out as EX legs. If you’re having trouble with this combo, this method is 100% reliable. No timing or piano-ing necessary. No need to worry about LK Legs coming out accidentally.