Assuming you are choking it correctly, I would start with the battery. You have to have over 12 volts from your battery for the starter to actually start the bike. Anything less, the starter just spins. Hook some jumper cables to it, from a good battery, and see if it starts any easier. If that works, you need a new battery. If that doesn't work, it could be a myriad of other things. Spark plugs, carburetor may need to be cleaned, or may have a vacuum leak. I would put about 4 ounces of Seafoam per tankfull of gas for the next couple of fill-ups, sure wont hurt anything. Seafoam is like magic in a bottle for fuel systems. When I bought my wife her 650 this past March, a new battery fixed what sounds like this same problem.
I don't have to have fast, I just have to have fun!