See Champion service bulletin SB1-15A:
The distributor gear shown in your picture has a copper electrode and is called out in the sb for removal. It should be replaced with the new design that has a monel electrode. I know we don?t have to comply with service bulletins, but you are anyway with the 500 hour inspection. You can purchase the new one from aircraft spruce for 113.75. Champion will reimburse you the cost of the part, but the return has to be handled by the distributor - aircraft spruce - so talk to their service department and reference the Sb.