Harley-Davidson is about as all-American as companies come. The motorcycle maker has survived wars, the Great Depression and a century of technological change. When things looked darkest in the depths of the financial crisis of 2009, the company got a lifeline loan from Warren Buffett.

Yet, the stock may have just begun one of its roughest rides in some time. Harley-Davidson shares fell 6 percent in midday trading Tuesday after it surprised investors by slashing its shipment plans. The company now expects shipment growth of 3.5 percent to 5.5 percent this year compared with a prior target of 7 percent to 9 percent.