I have seen a few of these come through with major crank bearing failure(I check every one that comes in before any other repair is done!) if the area around your recoil is oily at all, pull off the recoil and grab the pawl/catcher assembly with your hand and see if you can feel any up and down play.....if so.....buy a new unit......sorry not a fan of this model from echo. Posted via Mobile Device
Does it run better with the choke half on? If so its the mixture screw. They usually last about two years from factory then they get dirty and won't make power. I have 5 of these. 3 I bought off for cheap off guys who thought they were junk.
To fix you have to set a small drill bit to remove the small plastic plug on the side of the carb. Then you will see a flat head screw mixture plug. I take them out, clean the plug and hole then put back in. Start it and adjust screw to get the best idle. Too far in or out and it will go lean or rich and idle will got down.
Another option is to replace carb but it will crap out in a year or so.
This is part of the annual maintenance on our 755s now. They run great.