That's immaterial.

The store took the OP's money and there's an implied warranty of fitness for purpose. that means they have to deliver a working bike or refund his money. So, the OP should bring it back and say simply "it's doesn't wok right, please fix it", of course explaining the problem as best he can.

It's up to Walmart to put up or shut up (so to speak) and deliver a working bike, or offer a refund.

BTW - most Walmarts don't assemble bikes using general store staff. They use outside contractors who assemble bikes for a flat rate fee. So, they'll usually take the bike back, and ask the assembly contractor to fix it on his next visit.