Jamis ebike internal hub sprocket question
I have a Jamis commuter with an internal hub 8 speed Shimano Alfine rear and a front hub motor. I just use it around my neighborhood and for short distance shopping. It has a 23mph top speed with full power but I can't pedal fast enough to add any muscle power when I'm flat out (the front crank just spins freely at top speed). I'm an old dirt bike rider and we frequently changed sprockets for more speed or more grunt. The bike currently has a 42 tooth front and a 20 tooth rear sprocket. Can I gain a little more top end (while pedaling) by changing to a 16 tooth or 18 tooth rear? Rear sprockets seem to be cheap and available on Amazon. Be gentle; I'm a noob!