They adjust these things so lean, it may just be a carb adjustment. However, the carb may not be adjustable by you without damaging the special caps they have on them now.

I had the same happen with a friends chainsaw just yesterday. Fortunately, the carb was an older adjustable style one.

Sound's like it's to lean. If it has always been like this I would suspect a carb adjustment is in order. If this condition started suddenly I would check for loose carb mounting screws, loose jug mounting bolts, then try carb adjustments.

More info describing the problem would be helpful. Does it start & idle OK? Did this happen suddenly or has it always been a pita? Can you get it to high speed, then take the choke off and have it continue to run?

yeah, it used to run great! It will run on "no choke" & rev up fairly well, not like it used to though. Then if you gas it, it dies, so I run it on "half choke". If it's on "no choke" it does idle but will die by itself as well as if you gas it. On "half" it idles a little rougher but won't die. It also revs up on "half". It starts on 3rd. pull, 1 pull on "full choke", 1 on "half" then starts on 3rd, still on "half" like it always has since new. Mixture is 40:1 just like manual says but I'm thinkin' maybe I've gotten some of that *&^@#$%%** ethonol mixed gas. What you think?

I'm assuming the gas is fairly fresh and that's not your problem. I personally don't think ethanol is as bad as it's made out to be, it's being used as a catch-all for any engine problem. Now back to your problem -

Remove the air cleaner and make sure the carb mounting screws are snug. If that's nor the problem then proceed below.

These units use Zama carbs with high and low speed adjustments as well as an idle speed adjustment. I have seen the carbs with plastic limiter caps on the screws and also with no caps, but no slots cut in the screw either. I believe your problen is the engine is running too lean at idle and when you gas it, the mixture goes way lean and the engine dies.

Your objective is going to be to richen the idle mixture. If you have plastic caps these allow some limited adjustment. Turn the screw located closest to the engine (furthest from the air cleaner) counter-clock-wise 1/4 turn or as far as the cap will allow. This should fatten up the mixture a tad and might get rid of the bog when the throttle is snapped open. If you have the "no slot" type screw you may be able to use a butt type wire connector to grab the screw and turn it. A 1/4 turn should do it, if that doesn't work a carb cleaning may be the ticket.