I find the same thing sometimes. It varies with different 510 atomizers as no two atomizers are exactly the same. To start with, I do not like a standard Joye 510 @6V. I like it at 3.2-3.7 volts, and then once the atomizer starts to trail off on its vapor production I will switch it to my 6V
mod and it will perform awesome for a few more weeks. I don't clean them anymore either. Usually when I get the burned taste it is a new atty. I end up blowing it out and flooding it with the flavor I want in it. Vape it for a while keeping it somewhat flooded. After a little while, the burnt taste is gone and then I vape it normal. When it starts to taste a little off/burnt at that point, it is usually because the atty is dry. Hope this helps. If you have a 6V
mod, can you get a battery that will wun it @3.7? As you don't mention which mod you are running...