Last year I bought a 125cc bike, Modenas brand, most likely unknown to you. It is a moped.
http://www.modenas.com.my/v2motorcycle.asp?id=70
It can go as fast as 110 km/h enough for the city,
However, I gave it to a family person for a while and nearly destroyed it! Luckily the frame is ok and the bike goes straight.
He destroyed the exhaust valve, and 1.5 L oil consumption per 2000km! 1L capacity.
When I noticed it after 200 km running on low oil about 600 ml were missing, believing that it was serviced and ok. He had removed the air filter, and put a noisy exhaust.
I don't want to say much but I fixed everything I had the tools to do. Professional technicians told me that there is a problem with the piston/ring/cylinder.. and that it needs to be fixed... So I did... Cylinder got larger by 0.5mm ...
Here are some photos of the old piston... Do you see any problem with this piston?
Because i find that is has little problem an cant explain how this condition can cause so serous oil consumption problem?
http://dl.dropbox.com/u/4499990/sites/IMG_3760.JPG
http://dl.dropbox.com/u/4499990/sites/IMG_3761.JPG
http://dl.dropbox.com/u/4499990/sites/IMG_3762.JPG
Until now, after the service it seems to be running well... Oil level seems stable for the first 200 km.