Shares of Harley-Davidson Inc.rocketed on heavy volume Friday as reports of takeover interest circulated at a time when bearish bets were at multiyear highs.

The nearly 20% surge was the stock’s HOG, -2.05% best one-day performance since it shot up 20.5% on March 18, 2009. Volume soared to 23 million shares, which was more than 10 times the full-day average, and the highest level since Oct. 20, 2015.