Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: China Yuchai International (NYSE: CYD) dropped 10% in intraday trading today after an analyst made cautious comments about the stock in a research report.

So what: After touring a China Yuchai facility in southern China, Piper Jaffray expressed concern about the company's ownership structure and about truck demand in the second half of 2011. Piper Jaffray has a "neutral" rating on the stock, which many investors interpret as a recommendation to sell.

Now what: Piper also noted that it came away from its tour believing China Yuchai "is head-and-shoulders above the rest of our US-listed Chinese stocks when it comes to brand recognition and customer acceptance." Nonetheless, news about slowing economic growth -- including in fast-growing China -- can't be helping the stock. Nor can recent concerns about the reliability of financial statements from companies based in China.

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