1. Remove complete assembly from bike.
2) Remove engine after unscrewing four bolts.
3) Remove snapring from outboard bearing.
4) Send to machine shop. They will
A. Unscrew clutch drum and spacer.
B. Remove friction roller and bearings from engine housing.
5) Press outboard bearing into channel with snapring on inside.
6) Press inboard bearing onto new roller with snapring on outside.
7) Carefully press roller into housing from engine side. Snapring will bottom out in the housing.
TIP#1: You don't need the roller to press-fit into the bearings. Light sanding on the roller will allow it to slip onto the bearings easily.
TIP#2: I haven't tried this yet, but I WILL, the next time I need to change rollers or bearings. If you clearance the engine housing just enough so that the bearings can PUSH-fit, it'll be MUCH easier to replace or change the size of your friction rollers. Then you'll have to have BOTH bearings' snaprings on the outside of the engine housing.
TIP#3: Machinists charge an arm and a leg to R&R friction drive stuff for me. It is cheaper for me to buy a new clutch drum, spacer and bearings than to have them removed and reinstalled.
TIP#4: Vendors charge $12/pair for bearings, $30 each locally. You can buy them here much cheaper:
http://www.mfgsupply.com/m/c/AZ8205.html?id=5hP6hLJV
TIP#5: I know this one guy who drilled two 1/4" holes straddling the outboard bearing. Then he bolted on his steering wheel/gear puller and PUSHED the entire drive assembly out of the housing. He also pressed the bearings into the housing this way.
TIP#6: I knew this other guy who used a hammer instead of a puller.
TIP#5: Install new bearings when changing rollers. At $4/pair you can't go wrong.