It's a bit hard to explain..........when a two stroke is sputtering or running slow it sounds like a 4 stroke engine (firing on every other stroke)
open it up and the engine "breaks" into a nice two cycle sound.
It's easy to understand when you hear it....
Did that help at all?? LOL.
you will know when its 4 cycling, it goes buda buda buda buda, hahaha well thats how it sounds to me, anyways if you have a problem 4 cycling like i did then you will loose power and the engine will sound deep and low and will be rumbling, like a 4 stroke,