Sen. John F. Kerry, the Democratic presidential hopeful, spent yesterday's break from campaigning strolling through a Lewis and Clark exhibit, then speeding his Serotta bicycle 10 miles. Then Heinz Kerry went to her Fox Chapel home to prepare dinner while the senator, an avid rider, made his first ever loops on the bicycle path in North Park. In professional gear, from bike-clip shoes to handle bar gloves, the senator and two secret service agents went two laps on the five-mile course. Not winded at all, Kerry then loaded his orange and yellow, 10-speed bike, which he often takes along on...