Man, a lot of you new guys lately have been sensitive sally's.
You need to realize something right quick. You came on here asking for information without giving any information, then kept trying to justify your lack of information by proclaiming that you KNOW the guy put the "good stuff" on it. Well, what he considers the "good stuff", might (likely) not actually be good stuff. Seeing something described on BansheeHQ as "racing carbs", and "racing clutch", immediately gets made fun of.
Also, are they aftermarket big bore cylinders? Or just stock cylinders bored over? You have contradicted yourself. If they are simply bored stock cylinders, unless they were bored and sleeved to a much larger size, you didn't gain any noticeable power by them being bored. Typically when stock cylinders reach 66mm, they are considered junk without proper sleeving done.
Additionally, why do you want a number on power? If the horsepower number is relevant to whether or not you purchase the bike, I would suggest taking it to a reputable shop with a dyno, and have it dynoed prior to your purchase.
You need to understand the amount of knowledge here is vast. If you want specific answers, you need to ask specific questions. The question you asked is simply unanswerable. There are literally hundreds of thousands of motor combinations out there, and with descriptors such as "racing carbs" you won't get an answer remotely close to accurate. What size carbs? What manufacturer? What is the jetting? What is your compression? What fuel are you running? What is the air temperature at the time of dyno? <--- Those among thousands of other questions will get you SORT OF in the right direction with a horsepower guess, but even still, it's just a guess.