how many hrs / gallons of fuel have you ran thru it?? what is the use of the motor? like crazy 3d hangin on the prop??? stuff like that.. very possible a bit of dirt got in there or it was run lean a few times.. if the top of the piston is black then it was lean (not doubting your ablities) but if the piston is scored so much that you can feel it when you lightly drag your fingernail over them then i would replace it.. also do you run after-run oil in it? check bearings may have one going / gone bad.. hope this helps

also do a search on the cylinder peeling episode.. the older ones had a problem with the chrome i think it was peeling how old is the motor? need more info
p.p.s- get an electric starter if you dont have one it will save you headaches!!