birdwatcher

I just bought a vintage singer 500a rocketeer. I oiled and greased it and found the fly wheel to be a bit loose, not loose as in coming off the machine, but loose meaning it turns loosely then seems to catch the gear. Am I making myself clear? When I start to sew, I need to turn the wheel slightly to get the machine going. During this "loose turning," the needle doesn't have the strength to penetrate the fabric. Is there a way to tightening the flywheel, or is this inherent in this machine?