imageIt didn’t take Yu Ben Meng long to find problems at the nation’s largest pension fund.

Six months after starting as investment chief of the California Public Employees’ Retirement System, he told board members at a Santa Rosa, Calif., gathering in July that some older investments might be valued too richly, said people familiar with the matter. By fall, the fund had shaved the value of a real-estate investment trust and was looking more closely at a five-plus-year-old bet on a solar developer, other people said.

The steps are emblematic of Mr. Meng’s overhaul of the $389 billion fund known as Calpers. Now as his first year comes to a close, Calpers has cut ties with a longstanding manager on a hometown project, jettisoned underperforming stock pickers, and slowed work on a multibillion-dollar private-equity experiment.