Echos are great engines and I really like them. However, if that is not a "twin needle" carburetor with both a high and low adjustment needle, you will need to change it for one that is. They make them both in the standard butterfly throttle type, and the rotary type like yours as well. Either one will work fine as long as it has both needles to adjust. Most of the rotary carbs like yours don't have dual needles unfortunately.

If yours doesn't have dual needles and you want to stick with the rotary style carb, try DavesMotors.com I agree with W8YE's size recommendation.

AV8TOR