From what I’m told, Fritz t. Cat is correct. It’s not really 12v you’re looking at from the motorcycle, but at least 13.8v or so with engine running and alternator/whatever doing it’s thing. I’m told that you’ll also see nasty spikes from various things that happen with an engine. Different sources make different claims, but I think the lowest numbers you’ll see thrown around for spike voltage are maybe 18v-20v.
That said, ImA4Wheelr hooked his [clone] up to a 3s li-ion pack over here: Mod - SolarStorm X2 Clone - Pic Heavy
I think you can probably get away with it with no mods at all. The inductor is not going to be what limits your voltage. In this case neither is the buck controller, the QX9920 can handle very high voltages. If I was going to worry about something it would be the SMD capacitors, the FET (s), and maybe the zener/resistor pair that power the QX9920 (an easy mod if necessary, just increase resistance).
Note that the clones and the real version do not share the same driver, but both are based on the QX9920. The “real” driver has an op-amp installed, I do not know exactly how the op-amp is powered or what it’s maximum voltage ratings are. It’s probably fine…