Intact Lithium Battery
The cheapest and easiest way to save the most weight is with the battery. Another advantage is the much smaller discharge and more constant starting current of a lithium battery. If you don't ride that often or just go to the track a few times a year, you won't want to be plugging in the battery all the time. Intact is known from racing with its own Moto2 team where Dominique Aegerter rides in MotoE.
The optimal charger for these batteries can be ordered. Attention not every charger can also charge lithium batteries.
Technical details:
LI-0312,8V, 4Ah, 48Wh 240A, 1kg
LxWxH: 134x65x92 mm
Japan Code: LTM14-B
Replacement for: YTZ10S = GEL12-10B-4, YT12B-BS = GEL12-12B-4, YT14B-BS = GEL12-14B-4, YX14AH-BS = 81401, YB10A-A2 = 51111, YB12A-A = 51211, YB12A-B = 51215, YB12B-B2 = 51212, YB12C-A, YB14-A2 = 51412, YB14-B2 = 51414, YB14A-A1, YB14A-A2, 12N12A-4A-1 = 51211, HVT-09