Just because you’re running a kicker only bike, it doesn’t mean you shouldn’t benefit from the technologies that have transformed batteries beyond recognition; and this 12v Absorbed Gas Mat battery measuring 150x65x93mm is just such a thing.
Gel-filled, they’re guaranteed not to spill or leak making installation possible in any position and location, are maintenance free and typically have a longer service life than a regular flood-filled lead-acid battery. They do offer less power at the same weight, but you’re not going to start much with 7Ah so that’s not critical.