pull bowl off carb. those two screws! poke float. sometimes (apparently, never happened to me) they can "rock" over and jam. who knows?
i guess ill go in depth now
first off. start by draining some fuel into a vessel, by pulling the fuel line off. if it flows then sort of stops or dwindles away... remove the fuel cap. if it returns to normal, its the cap. otherwise its the fuel tap or line. fuel tap is fairly simple to pull apart and check... some come with an internal filter...unscrew whole tap from tank and check that too... paint flakes in the tank will block ones without a filter too... wash tank if its got debris inside.
nothing wrong with the fuel flow from the tank means its the carb. first off, with fuel on... remove the one screw at bottom of carb. petrol only should come out. replace screw.
turn fuel on, let carb fill, turn fuel off. remove the bowl. with some careful fiddling you can do it, one; without removing the carb, and two; not spilling any fuel from the bowl! you want the fuel about flush (a bit over really) with the bottom of the RECESSED part in the bowl, with the float still floating in the bowl. the part thats there to clear the little hinge that you will see when you open it. that brings it to the right level when the bowl is reattached.
technically, as long as the jet remains submerged at all times...it doesnt matter how low it is.
if not, you have to gently bend that little fork on the hinge...bend up if the fuel was too low, and down if fuel is too high.
loosen carb off and spin on manifold, pull it off completely, whatever, so you can get to the jet easily. its made of two parts, the main thick brass tube...get a spanner and tighten that first, via the two flats on the end of it. the jet itself is the little bit screwed in to the end of that tube. it always annoys me when they come out together, so i tighten the main tube first...
remove jet, look through it. the hole is fairly small. but it should be perfectly round and clear... blow through it, make sure. replace.
remove the aforementioned hinge by pulling its pin if it hasnt already fallen out by now... its a valve. like in a toilet cistern. theres a little needle in there. remove, make sure the brass barb that the fuel line attaches to is clear... reassemble the valve hinge needle assembly the same way it came apart.
replace bowl. test ride.
curse because nothings changed!
jk