Crystalyte Journey kit

I installed a journey kit on an old Giant Karakorum mountain bike. Runs great but I expected more speed. Starts out at about 17mph and goes down as I ride. I ride 20 miles to work and it take about an hour and fifteen to twenty minutes. Not but but would like to be there in an hour. I have the standard setup with 36v 8mah Nimh battery pack, 408 motor and 20 amp controller. Is this the speed I can expect from a bike like this. My weight is about 215 and the bike with motor and battery is about 65 pounds. Does anyone have a setup like this and getting similar results?