Small Engines (Lawn Mowers, etc.): 3.5 horizontal B & S, oil deposits, christmas present

Question
I have bought a 3.5 B & S for my sons go-kart. the previous owner said that it sat up in his shop for about a year so he said. I found water in the gas and i know that the carb needs to be cleaned because it won't idle smooth. I have noticed there is a small amount of oil in the breather. my problem is that is dosen't seem to have enough power to take me for a ride, now I'm 200lbs. my son is only 40lbs. he hasn't ridden it yet since it is a christmas present, i'm sure it will work for him. Is the lack of power due to the carb or a scored cylinder?

Answer
If you thing the cylinder may be scored then you can remove the head pretty easy and visually check.  Another indicator of a scored cylinder is engine oil burning(bluish/white) smoke and the oil level will decrease at a noticalble rate along with oil deposits on the spark plug.

Eric