If there's only the bike it shouldn't be an issue, just fly-kick away. His standing A special usually does the trick if you're in the middle of the screen (to prevent being hit by them reappearing). Otherwise, it's crowd control, which Axel2 is fairly good at...does grand upper have immunity in it somewhere?
You may have not played the mod for sormaker I use to play since, modders like to put them huge life bar (2/3rd to full) and jump kick + standing special takes time to kill them, even with Axel I which deals double damage on his jump kick. If you add donnies into the mix... :-p On top of that, if you stay mid screen, they can use wheeling attack and I still don't understand how to time the jump kick to hit them while they lift their bikes (maybe there is some differences between bikers 2 and 3). So staying in the middle is the best way to get flanked or wheeled (?) lol.
If he had a longer special (like max or blaze) he could evade and deals damage to both mooks and bikers, but with Axel it's harder to get this situation so wasting special is not good at all lol.
Grand Upper (axel2&3) and Dragon Smash (blitz 2*: axel 1,2&3) has invincibility start up, but your character is still open to receive damage, and has bikers go "through" you, you're screw. Note that Max can use his off special if well timed since he goes across the bike while the bike go through him
(or his blitz 2 since it is god invincible and free lol). Thank for your input
Axel I would be the best of the three (range, damage, safe) if he didn't trade his jump kick for jumping knee. So we still have to choose between Axel 3 (jump kick + speed) and Axel I. Axel 2 is the worst of the three but still my main character (practice is the key!).