I am having issues with a cub cadet ags 2140 with a onan elite eh140 engine. It ran fine most of the summer then it wouldnt start. It ended up killing the battery trying to start it. I have cleaned the carb replaced spark plug and new battery and fuel filter. It is getting fuel and there is spark. It will backfire thru the carb when trying to start. I cant find a engine manual for this engine. Can these engines loose timing when not tore apart. Does anybody know what Briggs or Tecuhmseh engine would work in this mower.