It will only run at half throttle

There are a bunch of youtube videos about how to tune a 2 stroke carb. It sounds like the low speed adjustment is too rich, but you just have to try turning it in and out. Don’t panic, it’s easy.

CG

Check the screen in the exhaust muffler. If it's clogged up, remove it and throw it away. Put it back together and run it. Don't bother replacing the screen, I remove them as soon as I buy

The throttle on the echo carb works on a lifting mechanism. The throttle cable attaches to the top of the throttle and as the hand pulls on the trigger the cable pulls on the throttle. As the throttle turns, it is lifted and due to its design, the further it turns the higher the lift. The amount of air/fuel is regulated this way.

Sometimes a carb change requires a special look at the throttle to make sure it lifts enough for engine to run at proper speed. Pay special attention to the screw that sits under the throttle at the max opening. The throttle needs to lift up to pass over the screw head. Sometimes it hits the screw top and fails to open all the way thus less RPM.

Had same issue; found that new gas line was not properly inserted in tank completely simply reposition; the spark arrester screen completely carboned up; brake cleaned and tooth brush cleaned like new, now it runs like new I also did the whole tune-up kit (carb, plug, hoses- think it was carboned up screen all along); BTW make sure you put the hoses on carb correctly- good luck!!