he act in every instance is fuel being ignited b4 (or as it's) entering the combustion chambers. sometimes exagerated by reverse flow conditions. that's typical of "shooting out". other wise it just pops and there's a flame present. be it briefly till it's put out via continuous vacuum demand or the engine dies(i.e-no more fuel delivery). causes can vary.

"shooting out"

typically leaky intake valve or cam way out of time due to T-chain/belt issues or improper cam to crank indexing after maint pocedures.

just a pop and a flame,

but there are other causes. like floats sticking, depending on the carb maybe a gasket failure allowing free flow of fuel. these instances can be an acumulation of the right conditions. excess fuel and a hot intake can ignite fuel w/o having a leaky chamber due to valve seating. doesn't take much to ignite exccess fuel in the intake area once fuel is atomized.

prolly left out a few other examples. but you should get the gist of it.

Timing out. Bad intake valve.

Back fire, a timing issue.

Timing is off.