In fact, it won't accelerate at all.
You are going to have to reduce the engine speed by mounting a very small sprocket on the shaft, and driving a larger sprocket on a driven shaft (jackshaft) that has a small sprocket on the other end, which in turn will drive the rear wheel sprocket. I'm not sure you can do this without the first driven sprocket being very large so you get enough reduction in the final drive.
You won't need an expensive shift kit, but you will need a double reduction with a jackshaft.