http://www.youtube.com/watch?v=uf0AKO-_tI4&feature=youtube_gdata_player The 630 has a 510 head and is similar to the 250, 310, and 450's of this model of engine design. Even Coffee can adjust these and he made a video to prove it.
I forgot about that video Since I refuse to to provide a 'google account' I cannot even log in any more.. Update your YouTube account by linking to a Google Account You will no longer be able to sign in to YouTube without a Google Account. If you do not want to link this YouTube account, you can sign out here