You should be able to flip the clutch around or whatever makes the new sprockets line up with the jackshaft. I'm not sure what kind of hills you're looking to climb but from your other post it seems like the big motor and the TC setup is what you need. Unfortunately that's big money.
Otherwise i'd say 8.6 is a good figure. Should probably end up at about 18mph on top end just guessing.
Otherwise i'd say 8.6 is a good figure. Should probably end up at about 18mph on top end just guessing.