Very simple Mariner5 air-cooled 2-stroke runs fine on half-choke , dies on anything less. I've had the carb off and cleaned it (though, oddly, I couldn't remove the main jet which is held up in place by a plug in the top of the float chamber . With plug removed the jet seems to levitate in the threaded hole , it rotates but neither rises nor falls)
Gaskets seem fine .
The idle jet screw does nothing, by the way. If the needle were worn you would think it would assist, if anything, in keeping the engine running.
Something subtly wrong with the level of fuel in the float chamber? Float is not damaged (and it would have to float higher to starve the jet wouldn't it?)
Sucking air through worn throttle spindle? Doesn't seem slack.Next session perhaps a drop of oil on the spindle while it's running might effect a very temporary cure , or at least be seen to be sucked in , and prove the point.
Should I just adjust the choke control so that half-off is as far as it goes?
What more can I do?
Actually now that I see it in print I wonder if I have really cleaned the main jet if I've not removed it. It's had a soak with carb cleaner and a blow through that's all, though with a lamp shining through the carb I could see a pinpoint of light looking up-the-way through the jet.