I was wondering what the co2 emissions and particulate emissions are
for 50cc and 125cc scooters. We always hear that they are
environmentally friendly but the data is either nonexistent or very
hard to find to back these claims up.And what type of emissions does
an LPG scooter emit, in g/km. Useful websites would be handy.

On motorcycles now sold in the UK the exhaust emissions are now stated
on the registration certificate, in g/km or g/kwh,
on my 600cc Suzuki Bandit the emissions are: CO=1.542  HC=0.600  NOx=0.080.
this information was not quoted in the owners handbook or in any sales
leaflets, so would need to ask a motorcycle dealer for the correct
exhaust emissions for other bikes.