My wife is interested in a bike, so we found one on ebay that looks to be in great condition with only a few minor cosmetic issues. It has about 20K miles on it and was supposedly running up until last summer. It turns over but won´t start. The seller says that a shop told him it needs a valve job. I´m pretty proficient in the garage (rebuilt the carbs along with a few other issues on my 81 Honda Magna), but I´m not a mechanic. If that is, in fact, what it needs, what does that entail and is it worth it if I get the bike for a few hundred bucks?