i probably should change the spark plug its 11 years old now haha.
Really?
You must have got one of their prototypes, the Lifan 150 was released in 2008.
If your bike was running mint 2 weeks ago, why change the carby ?
With the new OKO did you buy a new air filter (Uni Filter ftw) and throttle cable to suit ?
The cable needs to have longer travel, and depending on what your previous carby was the air filter will most likely be a different size
And dont forget to oil the air filter too with some decent filter oil too.
You might want to pull your tank off and give it a decent flush out before fitting the new carby, adapter, filter, fuel lines etc
Remove the fuel tap and do the same there, and after you've cleaned it all blow it all out with compressed air, with it having had bad fuel in it.
and make sure you replace the fuel lines and filter as well.
The mixture screw adjusts the Air/fuel mix,
To tune it, you start the bike and let it warm for a couple of mins, then raise the idle up to about 1800rpm by turning the idle speed screw in, maybe .5 to .75 turns.
Then adjust the mixture screw in or out till the engine runs at the smoothest/highest rpm, just go 1/32 turn at a time, let the engine settle for 10 seconds or so, then adjust it again.
Once it is close to the smoothest rpm, try adjusting it 1/4 turn at a time.
When you think you have it set nice, then you can drop the idle speed back down to normal rpms and take it for a test ride.