Joel, it's been a while since you posted this question but I'll bite: stock racing bars--I'm assuming you mean drop road bars--are great on a road bike but problematic on a motorized bike for several reasons.
One is the throttle/brake relationship. I'd think you would want your brake lever only a finger span away from the throttle, not "lift and reposition" the hand in an emergency. Take a look at any motorcycle, the brake can be operated at the same time as the throttle. The delay from shifting hand position from gas to brake could mean your life.
Two: the road bar is designed for aerodynamics, not comfort or visibility--yours or others. The natural head position when on the drops is head-down--where you can't see ahead easily nor is it comfortable for long periods of time. At the speeds of a motorized bike both of these things are against you.
You could use straight tubing for bars but again, you probably won't find it very comfortable--for a different reason. You'll sit up straighter and higher so you will be able to see better, cars can see you better, and your back will love you--but your wrists will hate you. It's better to find a bar that has some pull back so that your wrists have some bend to them. Actually, having your wrists facing each other is the most comfortable.
Another thing about a manufactured bar is that while the ends are thin enough to hold levers and grips, but the center is thicker for strength. A piece of straight bar won't fit levers and stem. Besides, bars are really cheap, probably as cheap as a straight piece of steel. I seem to accumulate cheap ones all the time, so much so that I throw them away. Check with anyone who has a pile of bikes around his house or at a metal recycling yard, you should find one pretty easily.
john
