You don't have to split the cases. Just pull the flywheel, and stator plate. Drill a small 1/8" hole into the existing seal on opposite sides of the crank output shaft(don't go too far and damage the aluminum case). Then thread in screws(sheetmetal) that binds tightly in the holes you drilled. Grab the screws with pliers and yank, the seal should pop right out. Clean the sealing surface and tap the new one in with a rubber mallet/ deadblow hammer and a piece of PVC pipe that matches the outer diameter of the seal. Be sure not to hammer the seal too far in. Some bikes have a flange that the seal seats against, others don't, so I recommend measuring how far the seal was set into the case prior to removal and relplacing it to that depth. Reassmble and pat yourself on the back for fixing the problem. Hope this helps.