Unscrew and open the carburator after 6000 km, then clean it properly by air blasting all passages and jets. Reassamble parts with new gaskets.
Screw in completely pilot air screw (4) and reopen 1,5 turns for basic adjustment.
Turning pilot air screw to the right = enrichens, turning it to the left = weakens mixture.
Screw off airfilter fasting bolt, take off air filter, wash it in gasoline, moisten it with oil, sling off excess oil and replace air filter.

2=Absorber

3=Float Needle

4=Pilot Air Screw

5=Main Jet

6=Needle Jet

7=Sliding Throttle Stop Screw