It's the Motavia Ultratec, light aviation engines from Klaymor Ltd. of England.

-They offer some new beautiful line 4-stroke engines between 60 and 80 HP.

-The engine was presented at Sun-N-Fun, they are matched to Rotax 582 engines.

-The engines are water cooled with a front radiator. They have head valves, two cylinders, a built-in muffler and also superimposed reducing gear.

“Motavia / Klaymor”

From Appendix 9: The Klaymor group has made the Ultratec engine of which we have more photographs to see its architecture in detail.

“Several views of Motavia, including a demo” (PiP)