1976 R 75/6. Problem has been intermittent for a couple of years, now here to stay : Battery voltage 12.88 volts AGM less that 6 months old. When I hit the start button , battery voltage drops to app 5 V. Idiot lights also dim. Removed can from starter relay. When I hit the start button The contacts of the starter relay arc but never completely close. Normal ? Also, with ignition off and move the starter relay with hand can see a tiny arc between the contacts . Boyer Microdigital ignition. Never had problems with it for5 years. Help, please.