Ok thanks. I figured out part of my problem, I had wired my charging plug wrong so my charger wasn't charging the batteries.
I also found a sprocket at electricscooterparts.com I was able to order a 74 tooth, I also went down one tooth on the front, I'm hoping it will give a ton of torque and still go 30ish mph
I had looked at lipos bit in 48v they are pricey! I dis get a lipo 36v for my sons new bike (mx350 with suspension, upgrading from mx350 no suspension with SLA batteries