What top speed do you want for this scooter, and is 9.8HP a continuous or peak number? Most 48V Golf Cart motors i've seen rate between 4.5 to 5HP continuous.
I honestly don't see a problem with a fixed-gear for a scooter. Transferring that motor from a Cart chassis to a Scooter eliminates a massive amount of weight-with a Scooter you will likely have speed and torque to spare. Just play with the gear ratios until you get it right balance between smooth cruising and hill climbing.
As an example-I ran a WV 12V, 30A generator and a (borrowed)19.5V, 3.3Ahr Dewalt pack on my bicycle at a 4:1 gearing a few weeks back-I buried the needle(antique speedo only goes to 30MPH!) sprinted up a 10 degree slope and left the ground briefly at the top...
When I save enough for a real 24V NiMH pack at 24V, i'll have to go 6:1 at least!
Now, that VW generator has 1HP or less at 20V...see why I think you'll have power to spare on the scoot?
Have fun!