What oil does a 4 stroke scooter take?

hey guys i just got this sachs madass bike and im wondering what oil i need to get for it... and if i need to know anything else about it... and i just went out to start it and something really weird is happening.. i go to start it and it just sits there and idles if it even gets started then right when i twist the gas it just dies.. The guy i bought it from added a little add on to make it 70cc instead of 50 and it moved the choke down to the bottom so i was thinking it was the choke but its really weird its not like a on off switch its just a litle spring loaded flippy thing that only goes in one place where other chokes u can pick up or down or in or out... so i dont know if its the choke or what.. anyone know.. its freakin me out.. i just bought it today ran perfect earlier now i get on it later and it doesnt start... :(

15W40 is the suggested weight for most scooters. Small scooter engines work like mad, so the best advice is to change the oil frequently, really frequently! Most experienced riders will change the weight of their oil according to the season, if there is significant changes in temperature, lighter weights in Winter allow for quicker warming and therefore better lubrication at start ups.

The weight is not as critical as keeping clean oil in the engine! Anywhere between 30W to 50W is acceptable, just use common sense according to the environment you ride in.

It'll be in the manual. Failing that, if you're in a normal climate, any engine oil will do. 15 - 50 or there abouts.
It doesn't matter all that much.
However you have a fuel/air mixture problem. Sounds like the choke is stuck on.
If not, you need to adjust the carburettor. Have a look on it and you should see a screw. Get driver and have a fidle, turn it gently one way then another.
If you don't know what you're doing, find someone who does or take it to the shop. It's real easy to fix and won't take but a minute.