[madoc1]

quinn is correct on that smell. the rotten egg is probably bad gas. are you still using the oil pump, or premixing? it is safer to premix.at 40/1 for the first tank after the build, then 128/1. one ounce per gallon. you should drain the old gas and put in some new. then pull the line to the carb and check while turning over. you should see a steady stream.
after you pull the top end check the cylinder bore for scratches, grooves what ever. you can just replace the piston and rings if it looks good. a check is to take the piston and put in the cylinder and check the clearance with a feeler gauge on the side of the piston that no holes in it . the max clearance is .007". you have deglaze the cylinder before reusing it. we did this and ended up with 130# before break in. if you don't have the tools, you will probably be better off with the whole kit tho. be sure to replace the seals while you have it apart.