* Yuan weakens for second successive day
* Central bank tightens reins with weaker fix
* Rate hits strong-side boundary for fourth straight day
* Posts narrowest day trading range since early March
(Updates to close)
SHANGHAI, Nov 2 (Reuters) - China's yuan ended slightly weaker on Friday even after hitting the strong-side boundary of its daily trading band for a fourth straight day, as China's central bank tightened its grip on the currency with the weakest midpoint fix in over a week.
The central bank set the yuan's midpoint at 6.3045 per dollar, weaker than Thursday's 6.3017.
That marked the second straight day the People's Bank of China (PBOC) has set a weaker fix, and means the central bank has now held the midpoint virtually flat since Oct. 17.
The weaker fix meant that even though the rate reached the strong-side of the trading band, it still traded weaker than at any point on Thursday.
Traders suggested the central bank may have lost its appetite for further yuan strengthening and that the recent period of steep appreciation -- over 2.4 percent since late July -- may be over.
``Overall, I see the yuan continuing to rise but in the short term we may well see a bounce against the dollar,'' said a trader at a city commercial bank in Shanghai.
Traders said that central bank guidance in the form of weaker fixes and informal influence on state-owned banks had slowed the yuan's rise since mid-October.
The central bank had previously set a string of sharply stronger fixes, between Oct. 11 and Oct. 17, which allowed the yuan to appreciate strongly against the dollar to a record strong close of 6.2372 earlier this week.
The yuan opened on Friday at 6.2432 per dollar, weaker than Thursday's close of 6.2405. It held close to the strong-side boundary all day, posting its narrowest high/low day trading range in eight months.
The exchange rate can rise or fall 1 percent from the mid-point set by the central bank each day.
Traders said strong dollar selling maintained upward pressure on the yuan on Friday, pushing the rate to strike the strong-side limit of 6.2415 at 4.01 pm (0801 GMT), where it held until the close.
That marked the fourth straight day the yuan/dollar spot rate has hit the strong-side boundary. The limit was hit for the first time ever last week.
Traders said that the trend for the yuan to appreciate in the afternoon may be linked to banks ``waiting to see'' what happens in morning trading before off-loading dollars in the afternoon session.
Some analysts agreed that the central bank may have shifted its tack on yuan appreciation and that the currency may now flatten, or weaken slightly, against the dollar in the coming months.
But, the PBOC is unlikely to risk sidelining China's major trading partners by driving the yuan significantly weaker, according to a report by UBS Investment Research.
The dollar index rose overnight, maintaining its bounce since hitting a week low on Oct. 31. The yuan traditionally tracks the euro and other global currencies against the dollar.
(Reporting by Shanghai newsroom; Editing by Jacqueline Wong)