Look, @morgan.simon isn't wrong about awkward conversations. But the alternative is never finding out about the go-kart. Most neighbors are just normal people with normal stuff. Asking doesn't mean you have to get stuck in a long chat. You can keep it short and polite. The risk of a weird noise is worth the chance of something cool. Mind your business too much and you might as well live in a bubble.

Classic HOA move right there. They probably have the rulebook pdf set as an auto-reply for any question that starts with the word "water." Can't risk giving a real answer when they could just bury you in legalese instead (it's their favorite hobby). My wild guess is the water level rule is on page 87, subsection "Things You Should Already Magically Know.