Don't put up with these Ryobi and other 2-cycle string trimmers that won't start or take the throttle. You can get the special screwdriver-type tool for the EPA Lo and Hi mixture adjustment needle valves and adjust it to start and run fine. I had to pour gas into the air intake to get mine started and run it on half-choke. I contacted Ryobi about the special tool and of course got denied. I was on the verge of shooting the damn thing when I found out on another forum that you can get the tools many places, even ebay. Mine takes the 'Pac Man' type, so-called because the needle valve head is just round with a pie-shaped chunk out of it. After receiving the tool, I had the thing straightened out in two minutes.

After getting it started, use it until it's completely warmed up. I use mine with a blower attachment which is why I'm using it in the fall/winter. Leave it idling and put the tool on the LH valve, or Lo-speed, and turn it left to enrich the the start/idle circuit. Turn it until the engine speeds up and then begins to slow down. Now give it full throttle and do the same to the Hi-speed side. Open it up until it begins to '4-cycle' then close it a little to get your top end back.

Now, after a cold night in the shed, give it about five primer shots, set the choke and it should start in a few pulls and run right. You may have to fine-tune the adjustments over a few uses.

Counting postage, I spent $20 for it and it's the best $20 I think I have spent. It saved me from having to go buy a new trimmer as well as possibly starting a big fire shooting the old one and getting arrested for shooting in town. :( Plus, it saves me minutes with every use because it starts and runs normally without special effort and fiddling around. The needle valves seem to have strong springs under them so they hold the adjustments.