Tesla shares drop after revenue forecast is cut.

Tesla Motors Inc., the electric-car maker led by Elon Musk, fell the most in two months after cutting its revenue outlook for the third quarter because of supplier shortcomings and other delays in the production of its Model S sedan.

Tesla slid nearly 10 percent to $27.64 Tuesday after the company said in a regulatory filing that it expects to generate $44 million to $46 million in third-quarter sales, compared with analyst estimates of $83.1 million. The Palo Alto automaker now expects to deliver 200 to 225 Model S cars in the third quarter and 2,500 to 3,000 in the fourth, down from earlier estimates. Tesla forecast that gross margin will turn positive in the fourth quarter as production accelerates.

“Elon Musk is very concerned about quality,” said Alan Baum, principal of auto-industry forecaster Baum & Associates in Michigan. “He’s been driving every vehicle off the line. That’s an indicator of how important that quality issue is to him. He’s going to deal with those quality issues before the vehicles are out the door.”

The company said in its filing that “we have methodically increased our Model S production at a rate slower than we had earlier anticipated. Certain suppliers have experienced delays in meeting our demand and we continue to focus on supplier capabilities and constraints.”

The electric-car maker also said it’s making an all-new car “with new employees using new equipment.” Tesla now forecasts full-year revenue of $400 million to $440 million, down from $560 million to $600 million.

Quality issues tied to suppliers have dogged Fisker Automotive Inc.’s Karma, which failed to win a recommendation from Consumer Reports. The magazine’s tests showed flaws in the luxury plug-in hybrid’s interior design and reliability.

“Tesla is mindful of what’s happened with Fisker and they’re very concerned that there are no hiccups in their launch,” Baum said.

Already the company’s largest shareholder, Musk may buy 33,311 more shares, the company said in the filing. Tesla, whose investors include Toyota Motor Corp. and Daimler AG, said it now expects to exceed its plan to produce 20,000 of the electric cars next year, when it projected it would earn its first profit.

The company amended its loan agreement with the U.S. Energy Department and may need to do so again if it fails to raise enough money from investors. Tesla plans to begin repaying its Energy Department loans in the fourth quarter.