It won't start'. I have added fresh gas and changed the spark plugs.

make sure there is spark on spark plug

Clean or change air filter. Clean, gap or change spark plug. Empty gas tank add fresh gas with Stabil. When spark plug is removed pull rope several times to blow out cylinder. Spray starter fluid in spark plug hole before replacing spark plug. Clean outside of carb so choke works freely. Spray starter fluid into carb breather hole with air filter removed and try to start. if running replace air filter and cover. If no start disassemble carb and clean. If no start replace carb.

Not to sure without seeing or hearing it being pulled over. Compression? Very likely needs some carb work/kit.

dump all the old gas out, put in fresh stuff, sometimes you gotta change the spark plugs as well.
cheers bucky

you added stabil but did you run the gas out of the carb? Take the carb apart and klean all with carb cleaner, spray in all holes. Check the plug gap of the new plug while your into the unit anyway the gap should only be 1mm.
Dennis

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thanks

Change the crank position sensor

You need to make sure you have spark. Remove plug, connect spark plug wire, hold plug to motor to make ground. Pull recoil and take note if you have a blue spark on the electrode of the spark plug. If you do, then it is a fuel issue, most likely gummed up the carb. Try carb cleaner spray and fresh gas.

If you can get it to fire by adding a small amount of the fuel/oil mix directly into the air intake, then you have a fuel system problem and either the carb or fuel line are at fault. Depending upon the amount of use the trimmer has had, it can also be an ehaust port constricted with carbon.

With a new plug and fresh gas it should start. Check to make sure there isn't a kill switch turned off or that the gas petcock from the tank to the carb is on.

How did you check the fuel filter? Disconnecting it from the fuel line that goes to the carb is the best way, making sure the gas is turned on under the tank. Bleed off a little gas into a can or something just to make sure the filter isn't plugged.

The last thing I'd do is take off the air filter and spray a little starting fluid in the carb. It may start and run several times if there is old gas in there somewhere. Remember the bowl on the carb is probably still full of old gas. After some fresh fuel reaches the plug it should start and continue to run.

(You might drain the bowl on the carb of ols gas before you go any further)

Good luck!

Sirwriter