Andy,
The cam wheels are trapped between the front and rear cylinder cam followers, so nothing else required to maintain their axial location. In fact, you would not want to apply a side loading. If someone has ground material off the side face(s) of the cam followers, there may be too much axial clearance and the cam wheel. The cam followers rely on the side face rubbing against the cam wheel to keep them square (in rotation) to the cam. If there is too much axial Clarence with the cam wheel between the two cam followers, the followers may rotate too much and allow odd wear to occur on the cam and follower.
Doug