You increase the range by adding a second pack of batteries in parallel.
38 amp 60 volts 5x 12 volts
38 amp 60 volts 5x 12 volts
connect both packs in parallel
equals
76 amp 60 volts
I am assuming by amp you meant amp hour(AH)
You probably should repost your actually battery stats. Though the answer would be the same. To get longer range. You need to increase your amps per hour total of the battery pack.
Wait, why am I telling you this? You are admin hahah. You know this already.
EDIT: You could always play around with the bikes gear ratio for better range at the cost of starting power.