Hesitation in first gear?????

Ok,
This is going to be a general tech question. I've been working on my girlfriends Kawasaki ZX-6R and just got it running. It's a 95 that was laid down and just got some cosmetic damage. The bike was sitting for about 9 months and we just got it a few weeks ago.

This past weekend I did an oil change, put in new spark plugs, checked the air filter, drained all the old gas out of the tank and put in some fresh 93 octane. When I drove the bike before we got it, there was a horrible hesitation around 7000 rpm's. I would be in first gear and hit about 7k and the bike would hit a wall, then around 9000 rpm's it would buck and take off. I really haven't been able to check out and see if it's doing that in any other gears since the bike isn't street legal yet and doesn't have a taillight. So I have to just drive up and down her street. Any ideas?

does it do this in all gears??? it sounds like a carb issue..like either the needle is wrong and it is not making a clean transition between the needle and the main jet..if it is just in first gear..it might be electrical. Alot of bikes have a timing retarder ( I know suzuki does) that will retard the timing in the lower gears to make it less wheelie prone

I'll have to take it out in the day time and see if it does in all gears. I'm thinking it's something with the carbs as well. The bike sat for 9 months with old gas in it. I know the prior owner put a full yoshi exhaust on it and he said he installed a jet kit, but I don't know if it was ever tuned or not. So it could be a number of things.