Ok I see. When you operate the throttle control to choke, check to see that the choke slide at the outer end of the carburettor extends thus closing the airway off effectively.
Get the engine running as you have been and run it up to normal operating speed. See the large flat screw on the side of the carburettor? This is your mixture screw. Ideal setting is achieved by slowly screwing it in until the engine falters and then wind it out slowly counting the number of turns until it falters again. Count the turns back in half the number and that's where it should be set somewhere there. Fine tune this setting for best running.
See how you go and let us know.
Cheers.
Ps when you wind the mixture screw in, don't wind it all the way in hard, this will damage the seat.
