True, it just so happens that most of the four stroke engines are low output OHVs based on industrial engines… But there is (or rather was) two and four valve OHC out there as well. SA250 and Vampire come to mind. Many of the euro brands made some prototypes, Vortex for one.
I don’t think the Biland or Swissauto are made anymore though?
There was a US importer of four stoke engines and I found their website on wayback machine
https://web.archive.org/web/20130828090825/http://engines4racing.com/index.php?page=biland
(Incidentally, as a nerdy project I converted my 206 to EFI using parts I found knocking around from Swiss Auto’s EFI system. The Delphi ECU on the SA was expensive and not super trivial to tune, so I used Speedunio firmware instead. But I did use the throttle body, injectors, sensors etc. from the SwissAuto EFI system)
While I’m here I guess I might as well archive the images of the engines… I’ll do that in another topic…
… and here it is: