Road test: 2004 Buell XB12R Firebolt

Torque comes from the Buell’s big cylinders, but the linearity of the powerband is due to a couple of tuning tricks. The beautifully shaped, complex bends of the head pipes are up 0.25-inch in diameter from the XB9 to 1.75 inches for improved flow from the 219cc larger mill. The under-engine muffler is also different than its little brothers’, as it employs a computer-controlled valve called Buell Interactive Exhaust. The valve opens at low rpm for the best flow, then closes in the midrange for optimum torque before opening again at high rpm, responding via throttle position and engine speed.