How much to change registration on a motorcycle?

I bought a motorcycle a few months ago,and need to know about how much it will cost to change the name on the plastic registration card from the old  owner's name to mine. I get different answers when I ask Khmers - I think they are all looking for a "commission" to help me get it done. I don't mind paying a small commission, but I don't want to get ripped off!
Thanks for your help!

Hi madmax888 :)

I hope other members will be able to advise you soon ;)

Regards
Armand

Got it done. Cost me $250 and I still don't know if I got ripped-off or not.