Current setup is a DB30 old style, engine mods include gov out, performance air and exhaust. Gearing is a Max Torque 12T and sprocket adapter 58T. Tire size is 15” diameter with stock 5.00 wheel. My dad says I don’t need a jack shaft for two reasons: 50 MPH is enough speed for a bike built to go 25MPH and the JS won’t improve torque or top speed. I think the JS will improve torque and top speed. I’m under 120 lbs. Before I upgraded stock sprocket, I could get the front end up but was only reaching 44MPH. I mostly ride street. Maybe a torque converter is a better option for me? Need advice, thanks.