If they are rusty I sandblast them, then spin the moving parts as you use a blow gun to blow away any grit. Be careful not to sandblast the fine spring for the pin on the drive pinion. Also make sure that the pin and spring work OK. Sometimes the pin is rusted in place and must be moved and oiled to free it up. If you need to remove the pinion from the helix, you'll have to grind or bend the locks for the nut on the starter end of the drive. I use a coat of light oil on the helix and put a coat of grease on the spring and pinion teeth. Be sure to use a spring wound in the correct direction, and use new or very good locks to keep the two spring bolts from comming loose. Use a spring that isn't torqued out of shape, like stretched or bent.