This newbie-ism makes more sense when rewritten as: “I just spent all my money on this used bike, and now it needs a new chain. Do I really have to cough up the money for a sprocket, too?” As frequently happens when you are older and have more experience, you’ll need to deliver some bad news. Or, you could just be an a-hole and say: “No, you only have to replace your sprocket with every other chain.”