what oil do you folk use? how many km do i need on my bbk before i switch to synthetic oils?
Personal opinion, in that simple engine everything above semi-synthetic oil is overkill.
Just change it every 2000 kms, warm up engine for a few minutes before blasting away at full revs, check valves and ignition every 6-7.000 kms and that would be enough.
KISS (Keep It Simple, Stupid) principle applies here.
With most scooters everything will fall apart sooner than you will experience problems in regard to oil quality.
I have P250S, 11 months old, 8000 kms, and had engine block replaced due to crack and today it will have tacho/speedo replacement as it died on me yesterday. On Agility 125 in the first 14.000 kms only starter switch died. On every bike and scoot I've owned in the past 11 years, I had all sorts of issues related with pretty much everything, but never with oil or engine core itself.
If it will make you feel better and buy "peace of mind" for 10-15 US$ in extra price of oil you can use fully synthetic and ester oils but, like I said, it is absolutely not neccessary on such a simple engine, especially not under normal conditions.
If you plan to travel two up on 50 cc to Andes, or race 24 hrs of Le Mans, I might have a different opinion...