When you adjusted the low speed needle, did you readjust the High Speed Needle? A fully leaned out low speed needle should stall at idle. To properly set the low speed needle, you MUST readjust the high speed needle before trying the transition test. If you fully leaned out the low speed, then your running totally on the high speed needle, and your high end is probably VERY rich. You'll need to richen up the low speed needle and lean out the high speed needle to get back into the operating range. One way to accomplish this is to do the following:

With the engine OFF, set the throttle open about the width of a needle. Now attach a clean piece of fuel tubing to the fuel inlet. Blow through the tubing. With the low speed needle fully leaned out, you should not hear any air hissing through the carb. Now slowly back out the low speed needle until you begin to hear air hissing. This is close.

Start the engine, full throttle, set the high speed needle to peak RPM less 300 rpm to the rich side. If you have access to a tachometer, use it to adjust your settings. Now perform the transition test. Use the results to make low speed needle adjustments in increments of 1/8 turn or less, and reset the high speed needle valve before trying again. Keep making small adjustments until the engine transitions smoothly with no hesitation.

Good Luck!
Brad