Following a review of recent performances in the Pro Stock Motorcycle category, NHRA has announced that the minimum weight for the Harley-Davidson 160-cid four-valve combinations will increase 20 pounds, from 620 to 640. The increase is part of NHRA’s ongoing efforts at maintaining competition and parity within the category.The change is effective June 4, 2009, at the United Association Route 66 NHRA Nationals in Chicago, which is the next stop on the Full Throttle Drag Racing Series tour for Pro Stock Motorcycles. Buell (160 cid) will remain at 625 pounds, and Suzuki (101 cid) will remain at 595 pounds.