Russ, is this on the right side on a Series 1 machine? If the sleeve is the one with a strip of steel along 1 side that acts as the activator for the ignition pickups, it is held in place on the crank by a grub screw. The screw is often the same rusty colour as the rest of the sleeve, but just turn the motor over until you see it.
Once you've loosened the screw, the sleeve should be a loose interference fit. If it remains stubborn, try the usual persuaders, penetrating oil, judicious heat, judicious torque (but be careful not to damage the strip along the side). If it still doesn't come off, you might have to look for a bearing puller that will fit behind it.
When you DO get it off be sure to clean the inside and the outside of the crank to bare metal, and coat with petroleum jelly. When your grandson pulls it apart another 35 years from now he'll have no trouble.
Ken