[Volknochi]

The only way I know is this:

cd C:\android-sdk-windows\tools
adb devices
adb push asroot2 /data/local/
adb shell
chmod 0755 /data/local/asroot2
/data/local/asroot2 /system/bin/sh

Which'll result in this:
$ /data/local/asroot2 /system/bin/sh
[+] Using newer pope_inode_info layout
Opening: /proc/857/fd/3
SUCCESS: Enjoy the shell.
#

Which you follow up with:
mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system
cd /system/bin
cat sh > su
chmod 4755 su

Which'll give you the $ line you're looking for. I tried it the other way (the way you did it, to test) and all I got was the # symbol.