Unable to adjust carburetor after overhauling, engine idle

The fuel mixture and or idle speed may need adjustment. If yours is a newer trimmer and it has a two cycle engine, these adjustments are sealed by the manufacturer. Some adjustment tools are sold on line but finding the right one can be a challenge. It seems the manufacturers almost force you to take it to a small engine repair shop to make this simple adjustment. It was the EPA that forced manufacturers to seal these adjustments.

Idle screw should be a flat head screw right under the gas tank intake near the carburetor.

For all others with String trimmers, blowers and other 2 stroke style engines...
If no power on high, tends to bog, won't run once choke off, check these:

• Fuel Filter - It's IN the Gas tank; Just replace it
• Spark Arrestor at Muffler, it's a screen that tends to clog up and causes very restricted exhaust flow
• Spark Plug - again just replace it
• Carburetor, clean or install rebuild kit
• And adjust sorta hidden High/Low carburetor adjustment screws

Take a look here...

And here:

And one more...

Carburetor is probably gummed up inside. There are very fine needle-thin holes in the spray nozzel through which gas has to flow. if they are gummed up, you will have an engine that starts, but has no power. try to take the brass nozzel out of the bottom of the carburetor, it unscrews & may be kinda tight. but take it out & clean the smallest holes with a thin piece of wire. should work great after that.

This sounds very much like a blocked spark arrestor in the muffler outlet, or the exhaust port is blocked with carbon, remove the muffler and look up the open exhaust port for signs of carbon build up, somewhere in the muffler there will be a mesh gauze ( spark arrestor ) either clean this or remove it completley.

A very common problem with most 2cycle units. My guess is that these units are 12 to 18 months old, and probably just need a simple carburetor adjustment. Remove the plastic limiter caps from the carb and open up the low side (nearest to the engine) jet about 1/4 to 1/2 turn counter-clockwise. Some of the carbs that Echo uses are not adjustable at all, and therefore the carb must be overhauled with all new rubber or must be replaced. Don't be mad at the shop, that is how they make a living.
Good luck!

i prime the primer bulb but no gas fills the bulb

Echo thinks your actual model number is CS-550EVL. Page 14 lists the starting points for carburetor adjustment here:
http://www.echo-usa.com/pdf/documentation/CS550evle_010186.pdf
Additional manuals for you saw can be found here:
EchoUSA
http://www.echo-usa.com/documentation.asp
More choices can be found by typing CS in the model: window then clicking “Search”.

Once initialized this is the best procedure I have found.
Carburetor Adjustment by Madsens.com
http://www.madsens1.com/saw%20carb%20tune.htm
CW is leaner; to lean will destroy the saw. If over tightened closed (CW) the adjustment screw faces are easily marred; marred adjustments are difficult to impossible to set properly.
Clean the air filter; adjusting with a dirty filter can cause a run lean condition once cleaned and the saw run.
There are 2 wav (sound - idle & full – may not be highlighted) files that I find most helpful, I think you will too. HTH
Lou

It will depend on what type of carburetor you have. You can go to this website and enter your model and it should give you the correct settings. If you cannot find the info, start with each about 1 1/2 turns out and go from there. A little hit and miss and you will figure the correct setting. When setting the high speed, you want to hold the throttle wide open and slowly adjust the screw. It will suddenly start to run very smoothly, and that's a good setting for the high speed.

http://www.echo-usa.com/faqs.asp

check fuel hoses for tears as you prime make sure two screws are tight that holds the primer bulb