BACK-UP your files and Database FIRST!!

1) Open your /conf/_locales.php file

do this change:
[php]$db_config['connection_charset'] = 'utf8';[/code]

2) Go to your phpMyAdmin and change your MySQL's default to "unicode_ci_utf8" or something similar

3) Change your b2evo DB to unicode_ci_utf8 as well (or something similar)

4) Then run this script: (save it in a file first, then upload)

<?php
$conn = mysql_connect("localhost", "DBUSERNAME", "DBPASSWORD");

$printonly=true; //change this to false to alter on the fly
$charset="utf8";
$collate="utf8_unicode_ci";
$altertablecharset=true;
$alterdatabasecharser=true;

function PMA_getDbCollation($db)
{
 $sq='SHOW CREATE DATABASE `'.$db.'`;';
 $res = mysql_query($sq);
 if(!$res) echo "\n\n".$sq."\n".mysql_error()."\n\n"; else
 if($row = mysql_fetch_assoc($res))
 {
  $tokenized = @explode(' ', $row[1]);
  unset($row, $res, $sql_query);
  for ($i = 1; $i + 3 < count($tokenized); $i++)
  {
   if ($tokenized[$i] == 'DEFAULT' && $tokenized[$i + 1] == 'CHARACTER' && $tokenized[$i + 2] == 'SET')
   {
    if (isset($tokenized[$i + 5]) && $tokenized[$i + 4] == 'COLLATE')
    {
     return array($tokenized [$i + 3],$tokenized[$i + 5]); // We found the collation!
    }
    else
    {
     return array($tokenized [$i + 3]);
    }
   }
  }
 }
 return '';
}

?>
<META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=UTF-8<? //remember to change it if needed ?>" />
<xmp>
<?php

$rs2 = mysql_query("SHOW DATABASES LIKE 'DBNAME'");

if(!$rs2) echo "\n\n".$sq."\n".mysql_error()."\n\n"; else
while ($data2 = mysql_fetch_row($rs2))
{
$db=$data2[0];
$db_cha=PMA_getDbCollation($db);
if ( $db!='mysql' /* &&( $db=='mydb_x' || $db=='mydb_y' ) */ ) // limit to database(s) - $db=='mydb_x' || $db=='mydb_y' || $db=='mydb_z'
if ( @substr($db_cha[0],0,4)!='utf8' ) // limit to charset
{
 mysql_select_db($db);
$rs = mysql_query("SHOW TABLES");
if(!$rs) echo "\n\n".$sq."\n".mysql_error()."\n\n"; else
while ($data = mysql_fetch_row($rs))
{
 $rs1 = mysql_query("show FULL columns from $data[0]");
 if(!$rs1) echo "\n\n".$sq."\n".mysql_error()."\n\n"; else
 while ($data1 = mysql_fetch_assoc($rs1))
 {
  if(in_array(array_shift(split("\\(",$data1['Type'],2)),array(
//'national char',
//'nchar',
//'national varchar',
//'nvarchar',
'char',
'varchar',
'tinytext',
'text',
'mediumtext',
'longtext',
'enum',
'set'
  )))
  {
   if(substr($data1['Collation'],0,4)!='utf8') // limit to charset
   {
    $sq="ALTER TABLE `$data[0]` CHANGE `".$data1['Field'].'` `'.$data1['Field'].'` '.$data1['Type'].' CHARACTER SET binary '.($data1['Default']==''?'':($data1['Default']=='NULL'?' DEFAULT NULL':' DEFAULT \''.mysql_escape_string($data1['Default']).'\'')).($data1['Null']=='YES'?' NULL ':' NOT NULL').';';
    if(!$printonly&&!mysql_query($sq)) echo "\n\n".$sq."\n".mysql_error()."\n\n";
    else
    {
     echo ($sq."\n") ;
     $sq="ALTER TABLE `$data[0]` CHANGE `".$data1['Field'].'` `'.$data1['Field'].'` '.$data1['Type']." CHARACTER SET $charset ".($collate==''?'':"COLLATE $collate").($data1['Default']==''?'':($data1['Default']=='NULL'?' DEFAULT NULL':' DEFAULT \''.mysql_escape_string($data1['Default']).'\'')).($data1['Null']=='YES'?' NULL ':' NOT NULL').($data1['Comment']==''?'':' COMMENT \''.mysql_escape_string($data1['Comment']).'\'').';';
     if(!$printonly&&!mysql_query($sq)) echo "\n\n".$sq."\n".mysql_error()."\n\n";
     else echo ($sq."\n") ;
    }
   }
  }
 }
 if($altertablecharset)
 {
  /*
  $sq='ALTER TABLE `'.$data[0]."` DEFAULT CHARACTER SET binary";
  echo ($sq."\n") ;
  if(!mysql_query($sq)) echo "\n\n".$sq."\n".mysql_error()."\n\n";
  */
  $sq='ALTER TABLE `'.$data[0]."` DEFAULT CHARACTER SET $charset ".($collate==''?'':"COLLATE $collate");
  echo ($sq.";\n") ;
    if(!$printonly)
  if(!mysql_query($sq)) echo "\n\n".$sq."\n".mysql_error()."\n\n";
 }
}
 if($alterdatabasecharser)
 {
  /*
  $sq='ALTER DATABASE `'.$data2[0]."` DEFAULT CHARACTER SET binary";
  echo ($sq."\n") ;
  if(!mysql_query($sq)) echo "\n\n".$sq."\n".mysql_error()."\n\n";
  */
  $sq='ALTER DATABASE `'.$data2[0]."` DEFAULT CHARACTER SET $charset ".($collate==''?'':"COLLATE $collate;");
  echo ($sq."\n") ;
    if(!$printonly)
  if(!mysql_query($sq)) echo "\n\n".$sq."\n".mysql_error()."\n\n";
 }
}
}
?>
</xmp>

Change: DBUSERNAME, DBPASSWORD, and DBNAME accordingly.

5) Go to your blog's dashboard. Then go to the "Regional" settings. Make sure your active languages are "UTF-8" by editing each active language/locale and changing the "Charset:" to "UTF-8".

You should be able to afterwards. See for example: http://laibcoms.asia/blog/xindao (the blog name is in Chinese)

* Note: crash instructions. I'll add it to my list of ToDo articles ^_^