Start with the frame. Check the welds, replace any cracked parts. Strip the bike of anything that weighs it down – drop a heavy seat, use a thin tire. Refit a strong chain and replace the gears if they’re slipping. Fix the brakes so you don’t skid. Then paint it a dark color and keep the headlight low‑power to avoid attracting cops. You’re not a thief, you’re just fixing a bike to move fast. Done.