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I've had this saw for decades. Last year it would not crank and cylinder pressure gauge indicated bad rings or worn cylinder/piston wall. I replaced cylinder head (with piston and new rings) and it fired right up with full choke set. However, when I press the throttle trigger, it releases choke and motor dies. Gas is less than 2 months old and has premium 2 cycle oil added. I replaced old carburetor with new one and the problem repeats. I adjusted H and L carburetor adjustments by 1.5 turns out from stop for a starting position, but the problem repeats. My next and only step is to replace fuel filter. I am at my whit's end. And suggestions???????

tank1949 said:

Gas is less than 2 months old and has premium 2 cycle oil

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Are you using marine grade 2 stroke oil? Stuff you put in a 2 stroke boat engine?

tank1949 said:

I replaced old carburetor with new one and the problem repeats

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OEM carb or Chinese Amazon carb?

Most 2 strokes you crack the throttle while trying to start. And of course full choke.

Try pouring some 50:1 2 cycle mix into the carb throat. Pull on the rope. If the engine runs for a few seconds, it confirms spark and ability to run. All you need then is fuel.

Probably cracked dead fuel lines and a grommet.

Do you have a modern day spout on your gas can? Or is the top wide open and the bottom full of water, bugs, grass, leaves and dirt?

Spark is fine. Echo primum 2 cycle oil. Saw's instructions say crank in full choke (if cold) and after it starts and runs for a few seconds, depress trigger/throttle. Gas can is built into the saw(plastic) and sealed well. One OEM and one carburetor is Chinese. I didn't notice any line cracks, but I will recheck. thx

You need to replace all the fuel lines including the primer bulb and it's lines and the in tank filter and then test.
Lots of you tube info about how to.
You say they are decades old.

Either use OEM replacement lines so as to get the exact size OD and ID or a good grade of tygon of the correct sizes.

Pressure test the carb as well after overhauled.

If it has not run for awhile, I would be checking the crankcase seals. They may no longer be sealing the crankcase, allowing air to enter causing a lean mixture.

You mentioned the fuel filter. How old is it? As a general rule if an engine requires choke to run that is an indication of too lean a mixture or fuel starvation. Fuel filters can look pristine but be internally clogged. They are so cheap and easy to replace that I’d do that first. Even if it doesn't solve the problem, if it is old then not a waste of time/money in any event.

Oddjob said:

You mentioned the fuel filter. How old is it? As a general rule if an engine requires choke to run that is an indication of too lean a mixture or fuel starvation. Fuel filters can look pristine but be internally clogged. They are so cheap and easy to replace that I’d do that first. Even if it doesn't solve the problem, if it is old then not a waste of time/money in any event.

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if an engine requires choke to run that is an indication of too lean a mixture or fuel starvation.

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