I’m lifting this post straight out of The ADV rider thread I saw it in.  Too good to let it pass.  Thanks 1upand4down.

In 1973 my dad bought this 900 Z1 new. I was 16 years old and he would let
me ride it. He had other Kaw’s he would let me ride like a 69 and 71 500 H1’s.
But there was nothing like the Super four 900. He sold the Z1 in 1975 to a friend of mine brother-in-law and he sold to his son’s friend a few years later.
I bought the Z1 back in 2005 and did a complete restro. Took about 3 years to
complete but was worth every minute and dollar. My dad got to ride it some that year and he really enjoyed it. He’s 79 now and I’m not sure if he
will get to ride it any more but maybe. It’s suppose to be in the next issue of Moto Retro Illustrated magazine.