| hey mate! i had the same problem not so long ago!
2 things what i encounted and fixed.
1. my throttle cable, i put it in wrong.. there is a brass needle that goes down the guts of the black tube, now.. make sure the needle goes down the guts, then a top washer!!! then the spring!
- if you have got the washer, then brass needle then spring.. well the needle will only travle up and not back down!
2. once you opened up the float. as explained by glen, above all that you will find another moveing part that goes up and down! with gentle hands, move it up and down, now if it is jamming up, then spray some wd40 down the needle hole, looks like a pin kind of thing! once that un jams, clean the bowl and all that jazz (making sure the white float - the ridged side faces the moving part with the needle) and hopefully you can yell.. wahla! | 
