The cam slides down the crankshaft and is located by the same key. If you are lucky it will be the same type key as the bigger 35,45,55 HP brothers with a projection down into the cam slot. Pry off the cam with a flat blade screwdriver and remove the rest of the key. I don't think the cam will fit through the center hole of the timing plate. Then, remove the timing plate and points etc and clean the crap off it. I can see metal chips on the magneto laminations. These chips will get onto the cam and wear the points rubbing block.
Finally, lap the flywheel to the crankshaft taper and be certain there is at least 80% engagement of the hub and taper. Search past posts on lapping procedure.
I can not see it in the photo but someplace on the timing plate there should be two projections meant to hold a felt wick. However, some engines have two wicks, some have none.
This wick would ride against the cam and would normally be lightly oiled. If there is no projection or wick put a SMALL dab of grease behind each rubbing block between the cam and points arm. Remember: Too much lubrication will get onto the tungsten points arcing and fouling them.