This is one of those situations where messing with stuff will bite you. If the quad ran fine last year, and then this year it doesn't, adjusting settings on the carb is NOT the solution. All this is simple, you need fuel, air, compression and spark.
Case in point. I ended up replacing my carb. I have gone through the hassle with a 3 wheeler i had, buying anything but the actual carb that goes on it. So in this case, I bought a used polaris OEM carb. Installed it after I cleaned it with carb cleaner and brake clean. Ran like crap. I used compressed air also. Blew out everything. Still crap.
I took it off, took all the jets out of it, and dunked in in the gunk carb cleaner, for a couple hours. Pulled it out, blew it out, sprayed it again, reinstalled all the new parts, and bam, started right up and runs flawlessly.
The person who said Ethanol gas is the issue is right. It attracts water, and then it mixes with the alchohol in there, and causes all sorts of issues. Just regular carb and choke cleaner, or brake clean will not dissolve this mess, you need something stronger. Ethanol treatment is basically a chemical that creates a sheen on top of the gas. It is not the end all be all. And once you get water mixed in with gas with ethanol, NO TREATMENT reverses it.
If you ride it every day, great, run whatever gas you want, if you don't, run only no ethanol. My quad sat in my garage all winter, cranked right up this spring. I only use no ethanol gas. And even when I use it only in my 2 stroke power equipment, I still have issues.
I would take the carb apart and soak every jet and the main body in carb cleaner for several hours, then put it back together and see what you have. Set everything back to stock.