Service manual for the KS150 engine (engine type LX1P57MJ), document LXFD0901-054, dated April 2023 on the cover. Loncin files it under the SR150GT. The bore, stroke and displacement on its specification page match the SR150GT 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. 7 gives 9.5 kW at 8,250 rpm and 12.5 N·m at 6,500 rpm. The owner's manual p. 10 gives 10.5 kW at 8,250 rpm and 14 N·m at 6,500 rpm. We cannot verify which figures are correct.