Yard machine ym26ss straight shaft trimmer. New gas,

the carburetor needs adjusted or taken apart and cleaned most likely. also the muffler spark arrestor may be plugged

clean air filter or replace--new spark plug

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/david_2f6e03df6c124197

You still have a fuel filter, fuel lines and maybe a primer bulb to check too. Make sure you're getting fire to the plug and fuel.

When this happens remove your muffler and check to see that the spark arrestor screen is not coked up with soot. If not remove the spark plug and with the ignition switch off pull the starter a few times. If some gas comes out of the cylinder then the carb is flooding the cylinder. In this case you have to open the carb and check the ' check valve' to see if it is seating properly or if the spring is weak. This can be done by pressing on the spring and releasing. Attach a piece of gas line to the intake and blow with your mouth. If air is escaping the valve and spring needs replacing. Another problem could be a faulty solenoid not delivering a consistent flow of electricity to the spark plug in sync with the rev of the piston.

David check the spark plug first and then the air filter. If both of these are clean and the spark plug is sparking put some fuel into the block.see if it runs then.

check air filter and spark plug if good carb adjustment is needed or carb may be loose. could be bad fuel water in gas will cause this

If the spark arrestor has been cleaned then it could well be the muffler itself, or the exhaust port blocked, remove the muffler and check the port for carbon build up.

Hi David, bring the high speed screw out until it accepts throttle, regards Phil.

Pull the spark plug and hold the side against the engine while pulling the string. check to see if there is a spark you may need another person to help. Was the air filter oily when you cleaned it? If so you might need to remove and clean the carburetor.

Maybe a quick fix and maybe not
check your muffler the factory puts a spark arrestor screen that tends to plug after awhile
there is a little plate on the side muffler that needs to be removed to access the screen you may need a torx bit or allen wrench to remove
you may have to remove the back half of the plastic cover to access the screws
remove screen and clean with carb. cleaner or equivalent make sure you can see through it and reverse the procedure to put it back