Quite likely you need to (at least) replace the metering diaphragm in the carburettor.
Before you do that, you could try turn the mixture screws out a 1/4 turn to see if that helps. Your echo may have a barrel carby, in which case there is the low speed screw down the middle of the barrel (pretty poor description, so just ask if you need a more in depth explanation).
There are plenty of tutorials on how to remove the diaphragm if you are unsure. Basically, it is retained by 3 or 4 screws on the carby. Also, you should look at your fuel lines to see if there are any splits, and clean out the little gauze filter in the carby whilst you have it all apart.
Once you have done a few of them, you get the hang of these little cube carbies.
Regards
Tyler
