Tuning can change from day to day, even hour to hour. Different engines will react to variances in barometric conditions differently.
If your engine has been at the same needle settings for a while, yes the tune has changed. Especially if it was last tuned during warmer conditions. The engine is probably, slightly out of tune.
Before starting to reset all the needles back to factory settings do the pinch test. Pinch the fuel line 1-2 inches from the inlet nipple on the carb while the engine is running. Count how many seconds it takes for the engine to finally die. Your target is 3-4 secs. If the engine dies instantly, richen the LSN 1/8 of a turn untill it hits about 3 secs. If it takes lnger than 4 secs, lean it 1/8 of a turn until you reach the 3-4 sec mark.
From the way you are describing your situation, you are running too rich. I'm sure that when the engine dies, it makes a gurgling sound then dies ... Correct? Another sure sign is the hydrolock situation.
OK, once you can get the engine to take off without stalling you can start tuning the HSN. This would be a good time to get a temo gun if you don't already have one. For the AE .15, your target should be anywere from 220-240. That seems to be the best performance range for these units. Again, each engine likes to run at different temps/power band settings. Tune for performance, not just aiming for a temperature and think that it's in tune.
As you run the engine through some high speed passes, make note of the smoke trail and power. The engine will stop reacting to leaner settings at a point and smoke will disapear. This is a sure sign that the carb settings are too lean. Also, hard restarts are another sure sign of over heating.
If you do not have a temp gun, you can do the spit test to get yourself in the general ball park. Spit on the head. If it sizzles away, instantly, you're too hot. Richen the HSN. If it sits, you're too cold. If it sits for 2-3 secs then boils away .. you're good.
Also remember, after you redo the HSN, you may need to tweak the LSN a little bit. Do the pinch test once again and then judge the holeshot. If it dies right away, it's too lean. If it burbles then dies, you're too rich.
IF you ahve messed with the settings so much that you don't know what the settings are anymore, then you will need to reset the needles an retune.
As I said, atmospheric conditions will take your car off tune. The first thing you should do every time you take your car out is check the tune. At most, only minor adjustments should be made. Also check your glow plug. IF it hasn't been changed for a while, do yourself a favor and just stick a new one in before retuning. Hydrolocking can deform the coil in the plug.
