Ryobi stalls after starting.

Yep had same problem it would run for about 20-30 sec and then just stall.
solution is the diaphragm on the side of the carby I swapped mine for the same one in my blower and it fixed the stalling problem.
The diaphragm operates the fuel into the carb. loose fuel lines can cause similar problem.

I had this problem. Frustrating! Here's what worked for me. There are two little nubs next to each other behind the "start/run" selector (aka choke) area on the carburetor. They are jets for your carb that control fuel/air mixture. If the world was a sensible place they would have slots for a screw driver - but it isn't - so they don't. You can still adjust them though.

The jet further away, or to the right as you're looking at it; is the one you need to adjust. It adjusts the running speed air/fuel mixture. The one on the left is to adjust the idle. Adjust the running speed jet first because after doing so you may not need to mess with the other one - it may idle fine or idle better.

Some people use a dremel to make a notch for a flat head screw driver, other people track down and order the elusive tool that supposedly lest you adjust it (called a pacman tool? Weird.) Anyway, I didn't get all technical with it, I marked the little nub with a pencil line so I could see the position, and then was able to use a little pair of needle nose pliers I had laying around to grab the thing and give it a half turn counter clockwise. Counter clockwise makes it richer (more fuel in the mix), clock wise does the opposite ("leans" it out.)

So half a turn ccw on that, fired it up, ran just fine. Was able to chop up a bunch of fallen trees and branches from the snowstorm we just had in Eugene. Idles fine too where before it would stall out if I didn't have the choke on.

Try this before you toss it, rebuild the carb, or go through some other extensive procedures. It's super easy and worked great with mine.

Thanks to the other people out there on the internet who's tips with similar problems with similar trimmers/pole saws/etc. showed me the way! Hope my comment might save someone else the hassle I was able to avoid.

Have a nice day and good luck!

DO NOT REPEAT DO NOT BUY RYOBI JUNK I HAVE 2 NEW WEEDEATERS FROM RYOBI THAT RUNS BUT WILL NOT ACCELERATES....JUNK!! SAVE YOUR MONEY BUY A BETTER PRODUCT...!!!

BUYER BEWARE!!!!! I absolutely agree with stockhunter, DO NOT BUY Ryobi WEED EATERS AT ALL.. Yes you can easily fix the problem by changing the diaphragm. But mine is only 5 months old and I've only used it four or five times. JUNK.
Don't know what else to suggest simply not Ryobi. Cheap but ****. rather pay more and get one that will last. VERY IMPORTANT!!! check and verify service and warranty before buying anything these days.