Starts and idles and runs half speed ok -- dies off on full throttle fuel lines & filter ok has ffuel in tank good spark & new plug muffler & screen & ports open clean good compression

Hi Alex:
Odds are pretty good that the screen in the muffler is plugged with carbon. The back pressure will stop it from running.
My suggestion?
Remove the muffler. Clean all the bits in solvent and air blow dry.
Re-assemble and
Ta Da!
Cheers

You reported that most of the items I would've suggested, you have checked...
Good job.
A couple more things:

• Replace fuel filter, it's in the gas tank
• Check and clean the Spark Arrestor screen at muffler, when they plug up, it's a major restriction to exhaust gas flow
• And check and adjust High/Low screws at carburetor, video attached.
• And clean or install rebuild kit for carburetor

Good luck...

One more...

May I suggest checking along the fuel line and its attachments for a very minor air leak. The minute it sucks air it will stop. Check any rubber washers or O rings too.

May need to have the unit checked. Could be something as simple as a clogged muffler, air filter, fuel filter or engine wear or damage.

Check the following, and then clean or replace:

• Fuel Filter - Located INSIDE the fuel tank
• Spark Plug
• Spark Arrestor - at Muffler
• Carburetor - May need a rebuild kit

Also watch this...

and this one as well...

take the muffler off and run it after seeing that it runs strong open the muffler and clean the screen inside (it's made to open)

take the carby in to have it assembled correctly
the positioning of the gasket on the right side of the diaphragm is critical

Morning William:
Acceleration is the "L" needle, try 1/8 turn CCW. No better 3/16 CW.
Please install a new filter on the fuel line, you will be beat to death with carburetor overhauls if you do not.
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.
• Clean the spark arrestor and muffler; if the saw cannot exhale it cannot inhale.
• There are 2 wav (sound - idle & full - may not be highlighted) files that I find most helpful, I think you will too.

If you have more questions or need additional help please reply below and I will get back to you. Thank you for using FixYa and Good Luck. HTH
Lou

Fuel starvation - 'lean fuel' condition
Basic things to check:
1) spark plug
2) spark arrestor in muffler
3) fuel lines and tank filter
4) turn adjustment needles out (counterclockwise) 1/4 to 1/2 turn
Chain Saws:
5) check impulse tube and intake boot for cracks or leaks
*if all of the above are OK and/or do not improve performance then:
Remove Carburetor
6) replace gaskets/diaphragms
a) use a spray carb cleaner to clean jets, holes, and body of carb
b) fuel pump diaphragm goes against the carb body,
then the gasket towards the outside
c) metering gasket goes against the carb body,
and the diaphragm goes towards the outside

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae

Are you saying full throttle, or full choke? if full throttle, you should be able to set the idle up. the idle screw will be the one when you give it gas, it will be the screw on you'r throttle linkage. If full choke, maybe the spark arrestor is plugged. You can remove it by removing the muffler.It would be between the muffler and cylinder head. You don't need this to run.I hope any thing I posted will help.