The older CV is ABN where the new CVR is abc. They also make a .15 CV-X now that is ABL. You may have run it hot and burned the motor up. Take it apart and see how far the piston will go up through the sleeve. It should gt tight before top dead center so know where TDC is.
If it is tight then reset the carb. Check for paper gasket at back plate. Check for O ring below the carb. Check that it has a good seal at the front bearing and go from there. Also check that the carbs O rings and what not are good.
Iwill also note my CV with the ABN sleeve is looser then a CVR.