Ok, If it was me I would use my air line and the oil can attachment that it came with, what your trying to do is get fresh oil into the internals of the starter clutch, so turn your compressor up to max then shove the end of the oil can into the part of the gear that you can see in the hole in the engine, SPRAY, pull it out and turn the gear a quarter turn and do it again till you have gone right round the gear, let it soak for a few minutes then do it again, then try to start it, do this half a dozen times and see if it makes any difference, Oh and DON'T use car oil use motorcycle oil, keep an eye on how much oil you put into the engine as well as it all adds up and you can easily over fill the engine if your not careful.
something like this is ideal it's called a paraffin gun?