At nearly 6'4" and 190 lbs the bike isn't your problem, it's your barn door aerodynamics. I'm the same way, though a couple of inches shorter at 6'2" but I weigh about the same and I'm quite lean. Despite being down to 10% body fat I still have a 34" waist, I'm built like a playing card from my hips to my shoulders.
I don't have blistering top speed but I jump harder than most of the other guys I race against. I just started racing again last season on the track, used to race on the road but it's been ten years. My body is a lot heavier since I last raced. Whereas I once was a mountain goat I now prefer short races with explosive finishes.
I think I'm doing well by a combination of keeping my head and body as low as possible and the gym work I've done, primarily heavy deadlifts and squats plus plyos like box jumps.