Thousands of motocross spectators today will wend their way up the Washougal River past the sleepy general store next to the steel bridge at the Clark-Skamania line.Hopefully, say the store’s family owners, the fans won’t forget their wallets.This could be the busiest day of the year for Washougal River Mercantile, which is ready to welcome crowds of dirt-bike fans, riders and pit crews that will breeze by on the way to the 2010 Lucas Oil AMA Pro Motocross Championship at Washougal MX Park, a couple of miles up the road. The national race often signals the height of the summer season for the out-of-the-way country store.“Nobody gets the weekend off during motocross,” said Ted Fuller, 79, the Texan-born patriarch of a family business that employs his wife, Charroll, four of their six adult children and umpteen grandchildren.“We’re the only store around for 10 miles,” Fuller said.That’s why its racks are flush with snacks such as Doritos and the 36-foot-long cooler is stockpiled with ice-cold drinks. Day trippers and overnight campers alike will find gas, propane and sunscreen at the 5,000-square-foot mercantile. The store also carries a full line of groceries, hardware and fishing tackle, and features a delicatessen, a feed store and a gunsmithing shop.The Fullers say customer turnout from the motocross race is always critical to the store’s annual sales. But this year’s event, expected to draw more than 20,000 people, is more important than ever to the business, after a two-year slump due to the recession.