If you need help tinkering with the carburetor, this may help. Even if you do not have an identical carburetor, the float mechanisms are all so similar to each other in general operation that this should still help you out.
http://motorbicycling.com/f39/motorized-bicycle-carburetor-install-rebuild-302.html
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3 rules of carburetor repair:
1.
Everything must be very clean. The work area, tools, inner workings of the carburetor. The teeniest bit of dirt can turn a good working carburetor into a frustrating headache or worse.
2. Never over tighten a threaded part. A firm snug-tight is fine.
3. If a gasket or seal looks to be worn/ very squashed or ragged around the edges, replace it immediately! Remember, you are trying to seal in fuel and seal out dirt. An iffy gasket or seal has no business in or around a carburetor. Be sure that any replacement rubber parts are made specifically for use with gasoline/ fuel.