Does this sound like broken piston rings?
 

I have a large walk behind weed trimmer on wheels which is similar to the ones in the linked page below. Have had it for a long time. I can’t get it to start. I replaced the spark plug and air filter. The plug is the right gap as specified in the owner’s manual. The spark plug generates a reliable spark. I pulled the plug, connected the coil connector to the plug then grounded it to the cylinder and pulled the starter cord. The plug sparks just fine and consistently.

I removed the spark plug, sprayed ether directly into the chamber and put the plug back on, and all I can get from the mower is an occasional pop out the exhaust. I’ve done the same by spraying ether into the carb and get about the same result. The pull cord pulls with the same resistance it always has.

https://www.google.com/search?q=wheeled+weed+trimmer&espvd=2&source=lnms&tbm=shop&sa=X&ved=0ahUKEwjxwPvJmarNAhUOQFIKHSoADQs Q_AUICCgB&biw=960&bih=498#spd=10878342580971112337

Broken rings would not be my first thought. It sounds like you still have compression. I would perhaps consider the crank shaft seals as a better possibility on a two stroke as it will not draw fuel if they are bad. . Although it should have fired off on the ether when you directly put it in the cylinder through the spark plug hole. That product evaporates fast as well though remember. So I would try a little gas through the spark plug hole instead.

About the only other thing I might do. Is get he piston at top dead center and try to make sure spark timing looks normal. Usually there will be a magnet in the flywheel that should pretty much line up with a coil that way. Unless it is a real antique. Flywheel keys have been known to shear.

As they say if you have compression, fuel and spark at the right time engines will at least fire and usually run. I do not have a lot of experience with two stroke engines though. So you will get better information from those that do.

Did you check the compression?

Should do near 30-60 pound.

Are you getting a blue spark?

Thanks for the feedback.

I have never before seen an instance where ether will not cause an engine to turn over or even try.

I don’t have a compression gauge but it occurred to me that I can use my thumb as a partial test.

My recollection is that the spark was blue and ~ white, but my recollection for color is not great unless I make a conscious effort to remember the specifics of the colors.

I’ll retest for spark color and compression when I’m near the trimmer again. I’m some distance from it for the next several days.

Came across this place where I can get a replacement engine for about $150 and some engineering.

This looks way more efficient than messing with the current one.

Engines

Sorry I assumed all these machines were two strokes. You might have a stuck open valve from sitting.

Thank you Barry. I dropped the demon off at the local mower repair shop so they can analyze. I’m guessing you are probably correct. If so i'll get a replacement engine for it from the place I noted above. Unless, of course, the shop can fix for less