Not sure what this one is, could be a KZ900 but it also looks a lot like the engine in my old '93 Kawasaki Zephyr 750 whose engine can be traced to the GPz750 and KZ650.
This was a real show bike powered by an old Triumph Twin.
They had a more moder Triumph Triple powered machine too. Note the solid disc in the front wheel. That aids the bike breaking the electronic timing beam at the bottom and top of the hill.
A motley crew of hillclimbers all with balls the size of
And the kid on the end is 15 years old.