General Motors Co (GM.N) sales in China fell 4 percent year-on-year in July but the U.S. automaker said it remained on track to achieve an upbeat goal for profit margins this year in its second-largest market. GM and its joint ventures sold 229,175 cars in China in July, attributing the decline to model changeovers, according to a statement on its website on Thursday. The July drop compares with a 0.2 percent increase in June and a 4 percent decline in May. GM sales grew 3.3 percent in the January-to-July period compared with the same months last year.