Japan's Honda Motor Co. is building a $25 million motorcycle assembly plant near Columbus, Ohio.

The Iranian Development Bank has pledged up to $250 million toward a huge apartment and shopping center complex in New Orleans.

Indal Ltd. of Toronto has acquired Peachtree Doors Inc. of Norcross, Ga. Cost: $20.8 million.

Algemene Bank of the Netherlands has agreed to buy the LeSalle National Bank of Chicago.

For years, the money had been flowing the other way.

Big U.S. multinational corporations, eager to expand into European and Asian markets, built huge plants overseas - exporting American products and jobs. About all that came back here was some modest foreign investment in American corporate stocks.

But now, with the dollar's value near an all-time low, American property and businesses are a bargain - and foreigners are lining up to get in on the action.

Last year, foreign investment in the United States - transactions in which overseas investors own 10 percent or more of the operation - soared to a record $34.1 billion, up 11 percent from 1976. And the total is climbing again this year.

Over the past 4 1/2 years, foreign investment in U.S. businesses and real estate has nearly doubled, rising an average $3.4 billion a year from $20.6 billion in 1973. And that doesn't include an estimated $53.1 billion in foreign holdings of U.S. securities.

The shift has provoked mixed reactions. Would-be property sellers here are smiling, but there is fear about too much cropland falling into foreign hands and apprehension that the Arabs will gain a stranglehold on American arms production.

Actually, less than 1 per cent of all foreign direct investment has come from the oil-producing nations. The bulk - 67 per cent - has poured in from Europe. Canada has accounted for 18 per cent, and Japan 5 per cent.

Congress, responding to farmers' fears that foreigners will take over American wheat and corn supplies, this year passed legislation requiring overseas buyers to report their purchases of U.S. farmland in the Agriculture Department.

And some critics have called for a crackdown on bank sales. Federal Reserve Board Chairman G. William Miller testified last summer that there were 122 foreign banks operating in the United States with assets totaling $90 billion. (By contrast, total U.S. bank assets are about $1.2 trillion.).

But in general, Americans have welcomed foreign investment as a good thing, both for the U.S. economy and for overseas investors as well. What's more, analysts say the influx could help trim the U.S. balance-of-payments deficit. Direct investment is included in the total.

The boom stems from a series of factors:

The past year's dramatic slide in the dollar has made U.S. investments a bargain for European and Japanese buyers. With the exchange rate so favorable to foreigners, it's often cheaper to buy businesses or property in the United States. And inflation guarantees a high return later on.

The sharp decline in the stock market here has enabled foreign investors to buy controlling or partial interests in U.S. corporations at what amounts to discount prices. It takes far less money to acquire existing plants and equipment here than to build new facilities abroad.

With the deteriorated dollar making foreign imports so much more expensive here, many overseas manufacturere now find it cheaper to build plants here rather than export to serve the still-robust U.S. market. Volkswagen, for instance, has opened a new assembly plant in New Stanton, Pa.

Recent near-victories by communist candidates in Europe - and takeover threats by separatists in Quebec - have made many foreign investors juttery about the political climate in their own countries, and eager to turn to the United States as a refuge.

Some foreign corporations want to get a foothold in the United States as a hedge against the possibility that this country may take protectionist measures in coming years to keep imports out. With plants here in the United States, these firms could sell as American companies.

The surge of investment has come primarily in a few sections of the economy. About 40 percent of last year's total was in manufacturing. Another 21 percent was in trade, 19 percent in petroleum and 7 percent in insurance. The rest was scattered.

Moreover, analysts say the $34.1 billion total probably understates the full amount of U.S. assets controlled by foreigners. For one thing, some investments simply are missed by data-collectors. For another, many such purchases are financed here as well, and not counted.

In general, the big influx of foreign investment has been welcomed by Americans. More than two dozen states and cities maintain offices in Europe and Japan solely to attract foreign business. And U.S. unions work closely with investors. Their purchases mean new jobs here.

But the inflow has raised hackles in two areas - banking and agriculture - where Americans seem to be sensitive about the prospect of foreign ownership. The entry of a West German firm into Ohio last spring drew outcries from local farmers about "selling out" U.S. grain.

In truth, such fears appear to be overdone. A General Accounting Office survey of 25 counties in five farming states last summer showed that foreigners owned a minuscule 0.3 per cent of the total farmland in these areas, with little hard evidence that it's about to rise very sharply.

And economists point out that total direct investment here by foreigners still is dwarfed by the enormous holdings of U.S. multinational corporations abroad. In 1977, U.S. direct investment in other investment in other countries reached $148.8 billion - more than four times foreign investment here.

Moreover, most foreign investors take pains to keep a low profile here. Those who have been tracking recent acquisitions say foreign owners rarely make sweeping changes when they take over a U.S. firm. Many even retain U.S. management to run the company.

And those foreign corporation that build U.S. subsidiaries often end up Americanizing their operations here inspite of themselves. Volkswagen, for example, got a rude awakening last month when newly hired New Stantion workers staged a ministrike to demand full U.S. wages.

As historians are fond of pointing out, the United States always has welcomed - and even depended upon - foreign investment. It was British money that financed the early ventures of the U.S. oil and cattle industries. Foreign-owned businesses have been granted full rights since the nation's interception.

The list of foreign-owned companies doing business here includes some of the nation's best-known brand names: Shell Oil Co., the Nestle chocolate company, Gimbel's and Saks' department stores, Lever Brothers Co. and the Keebler biscuit company.

For all the strength of the past few years' foreign investment surge, most analysts are predicting that the boom will continue - and even intensify. As more overseas buyers venture into the U.S. market and succeed, other foreign investors will follow.

In many ways the trend is evidence that, for all the markets' caution over the dollar, foreigners still are bullish on America - and are willing to put their money on the line to prove it.