Japan’s transport ministry inspected Yamaha Motor Co.’s headquarters in Shizuoka Prefecture on Wednesday, a day after probing Toyota Motor Corp., over improper vehicle certification tests engulfing the auto and motorcycle sectors. Yamaha said earlier this week that it had conducted noise tests for its motorcycles under improper conditions and reported falsified data in another test, leading the ministry to order a halt of shipments of its YZF-R1 motorcycles. Four other companies — Toyota, Honda Motor Co., Mazda Motor Corp. and Suzuki Motor Corp. — have admitted to similar misconduct, signifi…