Citicorp, parent of Citibank, the nation's second largest bank had a 3 per cent gain in operating earnings in the second quarter to 86 cents a share from 84 cents a year ago. First half operating profit was up 2 per cent at $1.60 a share from $1.57 a year ago.

Net income, which includes both operating profit and the results of securities transactions was $104.1 million for the quarter against $102.8 million a year ago. For the half, it was $192.6 million against $192.5 million a year ago.

The bank had a $7.6 million loss in securities transactions in the half, mainly as a result of a wide-scale restructuring of its portfolio of-tax exempt securities.

Net write-offs on bad loans amounted to $70.7 million in the second quarter and $58.1 million in the loans have exceeded actual writeoffs first quarter, but reserves for bad by $78.9 million in the past five years.

As of June 30 total assets were $69.4 million, up 18 per cent from a year earlier.

Chase Manhattan Corp, holding company for the nation's third-largest bank, said earning after securities transactions had dropped 4 per cent in the second quarter from last year's figures.

Chase Manhattan's earnings after securities transactions in the second quarter were $29.6 million (92 cents a share) versus $30.8 million (96 cents) a year earlier.

Manufacturers' Hanover Corp. said net income was higher in the second quarter and first half.

Operating net income for the quarter came to $87.9 million ($1.23 a share) against $34.3 million ($1.16) a year earlier. Final net income came to $378 million ($1.27) against $34.2 million ($1.16).

For the half, the bank holding company had an operating net of $796 million against $67.6 million in the corresponding 1976 period. Per share earnings were $2.68 this half and $2.28 in the 1976 period in both cases.

The bank said it set aside $20.9 million for possible loan losses with net loan chargeoffs for the half, the set aside figure was $42.7 million, with the chargeoffs amounting to $35.6 million.

Most of the nation's other large banks have reported increases in earnings for the second quarter.

Chemical New York Corp. holding company for the nation's sixth-largest bank, reported a 15.8 per cent rise. Another New York holding company, Charter New York. Inc., parent of Irving Trust and several other New York State banks posted a 5.2 per cent gain.

In Chicago Continental Illinois Corp. parent company of the nation's eight-largest bank said its earning rose 6 per cent in the second quarter.

And San Francisco's Crocker national Corp, which owns the nation thirteenth-largest bank announcing 9.4 per cent earning rise.