Hi guys,
Last night I helped my friend fix his Agility 50. He had 29,000+ KM on the clock, an noticed his engine making a funny noise. Both valves were not sealing up well, but worse, was that the oil wasn't being pumpped into the top of the engine so the cam, valves, etc went a short while with no lubrication...
The plastic gears on the oil pump were completely worn out. I highly recommend that you pay particular attention to the oil screen when you start getting high miles on the scooter. You'll see chunks of gear in it. Might be worth just replacing as preventative maintenance around 20,000 kilometers or so.
I have detailed photos, and will upload them when I get a chance.
My friend's engine was not badly damaged. We replaced the oil pump gear and the valves. I also threw in a new piston, but only because it was faster/easier than cleaning up the old one.
~Josh