This was one of the only vintage bikes at the races this weekend, so I had to take a closer look. As you can see at first glance, it's an Astro. But it has a Kawasaki engine in it, which was a popular conversion in the eighties. Some would call it a Bultakaw. I prefer to call it a Kastro.
Anyway, this is built owned and raced by Glen, of Glen's Autobody. Nice guy.
Among the many mods on this bike, Glen ran an extra long length of coolant hose from the cylinder, under the seat and back to the pump, to help make up for running only one radiator.
This is some creative frame modification to accommodate the exhaust.