4 stroking

I've noticed that when the engine is pretty cold it will 4 stroke a bit when cold but after it has warmed up there is no signs of 4 stroking at any throttle position. Is this normal? Does this happen because of some thermal expansion of the metal or something?

Hey everyone, so my bike was four stroking for about 3 years, i finally decided to change that so i went out and got a nt speed carb, (i had an rt dax carb) and put the setting to the leanest on the needle and it finally stopped. it goes so much faster now!