Don,
Here's my humble opinion.
Are these the only things modified?
The light rods, crank and pistons don't really add power.
Before you bite me let me explain. The lighter rods and pistons aren't adding anything to the combustion process but the engine will rev quicker. I had this argument with a buddy of mine who went to school for physics. His answer was that the engine does indeed make more power because HP is a measurement of work done over time. When you lighten the assembly the same amount of work is being done, it's just being done in less time. Still with me?
Since the engine can accelerate faster it has more power but depending on what kind of dyno you use it may not show it. For instance, if you put the bike on an acceleration dyno it will read a higher output vs. when it was stock, but if you put it on an Eddie current dyno, one that loads the engine at a certain RPM and then takes a reading, you'll get about the same number you got when the bike was stock. That's got something to do with the way each dyno measures it's power. The acceleration dyno can measure how fast it's drum gets yanked up to speed, from that it knows how much power you've made. An Eddie Current dyno measures the torque of the engine and then mathematically converts that to Hp.
Rest assured that if you had the Yosh bike and another bike that makes the same numbers, the Yosh bike, with it's light internals would accelerate quicker than the heavy internals bike.
On a side note for anyone considering lightening their stuff, I was talking to Carrie Andrew last year at Pocono. I was grilling him on whether lightening stuff was a good idea and he acted as though he really didn't care for it. He said in a road race the tire can break free easier and that more throttle control is needed. He also said it would hurt your torque output. I think he meant you'd lose your flywheel effect. Meaning that if you were riding on a level road and a hill came up the bike would decelerate easier with the lightened internals, whereas the heavy internaled bike would keep going at the same speed longer because of the momentum of the heavy internals.
Something else to think about is control. In the last few years Kawasaki added weight to the clutch basket of their ZX-7. The reasoning was you could get on the throttle sooner and not worry about blowing the tire away in the middle of a curve.
Hope this was easy to understand,
Sorry for the huge post,
Jamie
