Yes i would re check all the back plate gaskets, and the one around the carb. I would also sugest you try to turn the engine over with your finger, by turning the fly wheel. If there is little to no resistance, then you need a new piston an sleeve. Also check you glow plug, it could be fowled out. Also make sure that the head screw are tightened down properly. if there tightened down improperly,this could also be a leading cause of you problems. If you have any more questions just ask.