I would suggest the 83 shadow battery has died...possibly the redline issue vibrated the battery to death or loosened a poor connector/contact....maybe check the battery terminals.
The GS sounds like fuel related...pull the plugs and check them....the carbs probably need a good clean....I would be tempted to run some good carb cleaner through first to see if that helps. An oil change shouldn't harm any seals....if they are going to fail they will no matter if its got new oil or old.....although the old oil may be contaminated.
I would be checking the oil for fuel contamination and level. If its high then more than likely you have had fuel leaking and its run past the rings into the oil. Another possible issue may be a very high float level in one or more carbs.
Being such an old machine you may find the float needles worn...a small ring around the tip will indicate a worn needle.
What mileage do the bikes have and if its high then it may be time to do some remedial work such as bore wear and top end work such as valve seals etc...
The GS sounds like fuel related...pull the plugs and check them....the carbs probably need a good clean....I would be tempted to run some good carb cleaner through first to see if that helps. An oil change shouldn't harm any seals....if they are going to fail they will no matter if its got new oil or old.....although the old oil may be contaminated.
I would be checking the oil for fuel contamination and level. If its high then more than likely you have had fuel leaking and its run past the rings into the oil. Another possible issue may be a very high float level in one or more carbs.
Being such an old machine you may find the float needles worn...a small ring around the tip will indicate a worn needle.
What mileage do the bikes have and if its high then it may be time to do some remedial work such as bore wear and top end work such as valve seals etc...
