Carb issue
Not all NO START or POOR RUNNING is carb related. First you should determine if your engine is air tight. If you have an air leak in the crankcase it will cause poor ingestion and distribution of fuel. Make sure all of the screws in the rear of crankcase are tight, If you have a bolt on cylinder this should also be tight and properly gasketed. The carb gaskets must be installed properly and the carb torqued so it doesn't distort the carb flange or gasket, and the crank bearings in the front shaft housing have sealer around the outer portion of the races. If all of these factors are correct then your carb concerns are most likely correct.