I've been getting a nasty burnt taste on on 510 lately and it looks like the filler at the top of the cart wasn't getting enough liquid for the atomizer. I had to either wait longer between puffs or had to add few drops of liquid to it to get it wet enough to vape. What a pain but then one day I accidentally took a couple of drags without pushing down on the battery button and I got a mouth full of juice and when I activate the battery the burnt taste went away. Now I take a couple of short drags before I push the battery button to activate the battery. I have not gotten the burnt taste since I've been doing this except when the cart went dry. Those of you who has this problem give this a try.