Charon
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I think Bill is both right and wrong. A broad power band makes the machine easy to ride, while a narrow power band and lots of gear selections makes the machine (given a competent rider) faster on a track. The four-valve head gives better breathing at higher engine speeds, while a two-valve head usually gives better torque at lower speeds - where most car engines run on the road. There are at least a couple of automotive engines on the road which deactivate some of the valves at low engine speeds to try to get the best of both worlds.
A tuned pipe, either on the intake or exhaust, tends to make the power band narrower, because of resonances in the pipe. The reason expansion chambers on two-stroke engines are tapered is to try to widen the power band. A longer taper results in a broader and less "peaky" power band. A straight pipe is nearly the worst possible configuration in terms of being peaky, because there will only be one engine speed where its resonances match the engine speed. Motorcycle makers spend a lot of time and effort trying to make power bands usable over wide rpm ranges, which might even involve tuning the intake for one speed and the exhaust for another to smooth the torque curve. Fortunately, long-stroke engines such as the S40 and most of the V-twins have a fairly low maximum speed, so the job is easier.
The 0-60 and the 1/4 mile tests both are highly dependent on driver technique. The high-gear roll-on pretty much removes technique. All of the tests are dependent on driver and machine weight. All of them test the system only at wide-open throttle, and not much riding is done at wide-open throttle. In terms of carburetion, that means the only thing checked is the main jet. And for those with modifications, it will be very difficult to do a before-and-after comparison.
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