Why is your KX 125 bogging down?

Since it is a 2 stroke, you need to keep revving it every few seconds even when sitting still or in idle or the engine will shut off. It might also be because you need a new spark plug. It is located directly under the gas tank on the egine. Try pushing down the plastic cap on the plug, and if that doesn't work, just buy a new one for about $5.00