Cobra has made custom frames and chassis for the older type of Japanese motors for
Not so much a few years ago but they seem to have made a bit of a comeback now.
The photos on this page are a few examples.
Also Kavach Motorcycles from Tokyo on the links page show other Japanese bikes that
used Cobra frames to build some quite distinctive bikes, also undertaken now is various
modifications to modern street fighters including fuel tank work, modifier exhaust,
sub-frame and the like.