I have had good luck with Shorai batteries, having had them on a couple super bikes from the 1980s, the last couple years. As you've probably heard, if you haven't already tried them, they provide easy starting and seem to "never" require a charge if you ride often (and maybe even if you don't, as I have a couple bikes so equipped and I have yet to charge them, although I ride neither more than once/month and sometimes go as long as 3 -4 months without riding them.
Anyway, for my GT, I decided to give one a go. I called Shorai and the agent told me the LFX14A5-BS12 was the ticket. I have seen on line that that one or one other (larger capacity, more expensive) Shorai with a different number also works. The one shown is what I'm using and so far it seems to be a big upgrade over previous batteries I had in there.
True enough, gel and other "maintenance free" batteries other than lithium Shorai (and I suppose other brands) are ok (and cost less than Shorai) but I prefer Shorai because they seem to hold charge better and are MUCH lighter.
Bevo
Shorai Battery for GT 750
Re: Shorai Battery for GT 750
With a 750 the larger capacity the better. The reason is you will be less likely to run it flat in normal riding. The stock charging system on the 750 and early 860 is marginal at best. If the revs are kept around 3500-4000 the battery will stay up but putting around town especially with the lights on the charging output can't keep up with the draw. The solution is an ST2 alternator or at least the rotor but they are pretty thin on the ground now. I think Sparx makes a rotor with stronger magnets too. There are a few articles here on Bev Heaven about upgrades I think.
Re: Shorai Battery for GT 750
I got both stator & rotor for the early (single phase) ST2 from here:
regulatorrectifier.com
$340 US
regulatorrectifier.com
$340 US