im restorin a 1973 91 900, it was origanaly my dad´s. he sold the bike in 1980 to his brother, who for the last 25 years has let it sit outside of his gararge. I rescued this Z1 for 200 dollars. everything on the bike is stock except for the pipes, they are a 4 into 1 kerker header. does anyone have advice when re-doing one of these bikes?