You didn't get the whole old seal out. The outer portion is still in there. These are one of the easiest seals to replace on this bike if you have access to a large vice. You will need two small squares of plywood and a socket slightly smaller than the seal O.D. Test fit various sockets from the front side to find one that just fits down into the housing and against the seal. For the plywood, you need one piece large enough to cover and support the whole front of the housing and another slightly smaller to cover the casting on the rear that holds the seal.
For removal, place the socket on the back against the seal and the larger piece of plywood on the front of the housing. Sit this "stack" down in your vice and slowly tighten it. The socket will push the old seal into and out of the housing.
For install, place the new seal against the back of the housing with the small plywood piece on top of it. Place the large piece of plywood on the outside of the housing. Put this "stack" in your vice and slowly tighten. The little piece of plywood will push the new seal into the housing flush with the backside. It's actually a good idea to let the seal stand proud of the back by a MM or so. Just let the rolled edges of the seal back protrude. The cam stub doesn't stick out very much, barely enough for the seal lip to ride on. It's best to have the seal in as deep as possible, without hitting the cam bearings of course.
