First try a new fuel line, could be cracked. Also could be a air leak between the carb and cylinder or the seals. Steve

I agree with Steve plus what you have done and want to stress all mores:

1. More history should help: When did it run good last? Do you use ethanol fuel and if so is it treated with StaBil or etc gas treatment?

2. Did you find any deteriorated or not tight fuel lines fitting int or ext?

3. When you were in the carb, did you use compressed carb cleaner to verify "all ports and passages were open with compressed carb cleaner with adjustment screws out"? Did you clean the small fuel screen and below it?

4. Fuel in the carb does not verify it is getting the correct amount to run good. Usually blockage due to contaminated or old, sucking air due to bad fuel lines or bad primer bulb or loose carb to case or jug to case not supplying the vacuum needed.

5. Check the spark arrest screen in the muffler to know that back pressure is not part of the problem.

6. Usually if it will start from a prime but not continue to run, a fuel delivery is likely.

Tell us more and we might be able to help more.

the saw has been running good all summer . It just died and then would not keep running . I took carb apart ,cleaned all port and screen , changed gaskets and Diaphrams . I have taken off the Fuel line, intake boot, impulse line and they all look very good . All have good rubber and I can hold pressure in all three . Just put it back together and it fired up and ran for 2-3 seconds and then died and won't start now .

Can you post a pic showing the carb and as much fuel line as possible? I'm not familiar with the saw vs speaking from general 2-cycle troubleshooting basics.

1. Have you had success with repairs and maintenance before on the saw (carb cleaning and adjustments, fuel line and primer bulb replacement (if it has one)?

2. Have you checked the compression, which could relate to good fuel suctions, "I believe"? Help! Can any suction be verified at the carb, "Exp Techs" or is starting from a prime proof?

3. Have you pulled the muffler to check the cyl and rings for scores that would affect suc vs seeing smooth surfaces?

4. Back to an original question, did you verify all ports, passages were open while in the carb?

5. What Are We Missing?

The saw does not have a primer bulb , I have taken apart 3 different carbs and gotten all 3 to run .
Compression is good .
all ports were cleaned out

I checked and I have plenty of spark , the spark plug is firing on every pull . I tried to start it and it would run rough for a while but would never smooth out . After a while while running rough it would die .

I'm out of suggestions. Please post what you find as the problem, to possibly help others.

You might pull the muffler off and see if there's any scoring on the piston.

Took muffler off and everything looks good .