Service manual for the KS250 engine (engine type LX1P72MM), document LXFD0901-054, dated September 2023 on the cover. Loncin files it under the SR250GT. The bore, stroke and displacement on its specification page match the SR3 owner's manual.
The page references below use the PDF viewer's page count, including the cover.
Rated output differs from the owner's manual
The specification table on p. 6 gives 17 kW at 8,250 rpm and 22 N·m at 6,500 rpm. The owner's manual p. 11 gives 19 kW at 8,250 rpm and 23 N·m at 6,500 rpm. We cannot verify which figures are correct.