Leaping off the edge will cancel decay. Though I was mostly using jab-punches to refresh moves. All my 'Extra Aura' tests were done in Brawl mode, not training. So that shouldn't be an issue. The damage cap test was, however, done in training mode.
Now then.
*ahem*
Aura cap for each move! Yay!
Alright, I know what was fiddly about the previously reported 183% cap. Dsmash, like many of Lucario's attacks, deals a fractional amount of damage. That wasn't taken into account when trying to figure out what its cap is. That may very well be what's causing the damage difference in training and Brawl mode. You can't smack someone ten times in a row in Brawl mode to find the decimal damage of an attack.
Now then, my procedure in case anyone wants to duplicate what I found.
I smacked Mario ten times with each attack at 0% to get the base damage, then ten times at 999% to be darn well certain that Lucario's aura was as strong as it would get. Ten hits gets me out to one decimal place, which is enough for most attacks. There are a few that deal damage out to two decimal places, but that's low enough to ignore for the most part.
Now then, I would also like to point out that some attacks with higher decimal damage effectively hit their cap in the low 160's. But to get that last little bit of damage you need to get to the listed number.
Finally, force palm flame is odd.
Seriously.
At higher aura levels it has three damage points. The tip deals 11% and some change, between the tip and middle deals 12% and some change, and behind the middle and before the grab deals 14%. The exact cap there is somewhat wonky as a result. It might be different for all three.
Now to the numbers! (And attack names I picked! Any alternate suggestions would be nice!)
Furry Swipes: (A,A,A) 7%-14%, 170% cap.
Mega Punch: (Ftilt) 9%-18.1%, 167% cap.
Low Kick: (Dtilt) 4.8%-9.8%, 166% cap.
Rolling Kick: (Utilt) 4.2%-8.4%, 170% cap.
No idea >.> (DSmash) 9.8%-19.6%, 169% cap.
Focus Blast (FSmash) 11.15%-22.3%, 165% cap.
Dunno <.< (USmash) 9%-18.1%, 167% cap.
Nothing yet (Fthrow) 7%-14%, 170% cap.
Ditto (Uthrow) 4.2%-8.4%, 168% cap.
Comet Punch (grapple) 0.7%-1.4%, 170% cap.
Sorry (Nair) 7.7%-15.4%, 169% cap.
Double Kick (Dair) 11.15%-22.3%, 168% cap.
Iron Claw (Bair) 8.4%-16.8%, 168% cap.
Jump Kick (Fair) 3.5%-7%, 170% cap.
High Jump Kick (Uair) 7%-14%, 170% cap.
Lil' Aura Sphere 5.25%-10.5%, 170% cap.
Aura Sphere 13.1%-26.3%, 167% cap.
Force Palm Flame 6.2%-12.4%, 164% cap.
Force Palm Grab 9%-18.1%, 167% cap.
Double Team 7.7%-15.4%, 169% cap.
That comes out to an average of 168% as the cap. Though nothing goes above 170% in terms of where its cap is. So just saying that the cap is 170 would probably be the safest, most accurate bet.
And just post my data this time, Milln. People don't need to read mah ramblin'. =P