Some of the 140 sports have had an issue with the air bleed hole in the carb not being drilled out large enough from the factory. I have one that I couldn't get to idle smoothly at anything less than about 3000rpms. I called YS and a tech there told me to take the barrel out of the carb and drill the hole in it out to 1/8". He said some got out with the wrong size hole. I did, and my problem was solved. The 1/8" bit only enlarged the hole a few thousandths, but it made all the difference.

If you've got your air-bleed screw backed out all the way, and if the motor dies as soon as you remove the ignitor, then it sounds like the low end is rich, and I'll bet that's your problem. Take the carb off, take the barrel out, and check the hole size. If it isn't at least 1/8", I'd suggest you drill it out to 1/8" and try it. This is the hole that the air-bleed screw partially blocks as the engine idles, and if it's too small, you can't lean the engine enough to make it idle correctly. Once you do this, you'll need to make small adjustments to the high speed and probably to the regulator settings, too, because the idle circuit is always working when the engine is running, no matter what the RPM, so it affects the mixture at all speeds.

Hope this helps!

David