How to Remedy Your Stopping Leaking Float Needle Valve

Why is Motorcycle Carburetor  leaking fuel from bowl hose? Do you know what causes gasoline to drip out of the over flow tube of your carburetor?
The short answer is that a tiny piece of dirt is most likely stuck in the needle and seat of the float valve, preventing the valve from fully seating. Or else your float valve may need to re re-adjusted, or replaced (due to wear on the needle valve and seat), to lower your fuel level in the carburetor float bowl.
Even if there is no dirt in there, a metal-to-metal seal is not going to be dead tight. If you don't turn off the fuel at the petcock, the constant downward pressure of gravity will cause gas to seep past the needle valve and fill up the bowl if the engine is not running. You can get a bit of overflow seepage even under the best case if the petcock is ON. The moral is to always turn off the petcock when you park it or you may see a puddle of gas on the ground.
A good way to quickly flush off the carburetor float needle valves and seats, if one starts leaking, unexpectedly, without having to remove the carburetor float bowl drain screws, if it's on a motorcycle that has a fuel petcock that can be manually turned to the off position..
Turn the gas tank petcock valve off, if you have one, while the motorcycle is running, until the engine runs out of gas.
Then, turn the gas tank petcock valve open, again.. the gasoline will gush into the carburetors.. which will flush off the carburetor float needle valves and seats, with a flow of fresh gas, as the carburetor float bowls are refilling to reach their fuel level, again.
This method is meant, only, as a temporary on the road remedy procedure for helping you to try and stop your needle valve from leaking, to try and get you out of your predicament, if you don't have access to a screw driver, at the time, for removing your carburetor float bowl drain screws, which would be the preferred method, if you have the opportunity to do so.
Otherwise, try this procedure as mentioned, as you wouldn't have anything to loose, if your carburetor float needle valve is leaking bad, while your on the road.. as they say, nothing ventured, nothing gained.. then later as soon, as you have access to using a screw driver.. remove your carburetor float bowls drain screws and drain your fuel system thoroughly.
Some good advice to consider would be to install a good inline fuel filter, instead of just relying on the gas tank's fuel filtering system, which on some motorcycles is only a filtering mesh screen on the fuel tank petcock.
It would be well worth your time and effort to install a good inline fuel filter between the gas tank petcock and the carburetor's fuel rail.. which will eliminate any minute microscopic particles from getting down to the carburetor's needle valves and seats.. and these minute particles may, also, accumulate in your carburetor's pilot jets and main jets causing more engine performance problems.. especially as small as the orifice is in the pilot jet.. they clog really easy from inadequately filtered fuel..
Anyone who has had carburetor problems, before, knows how frustrating it can be, if you've taken the time to have cleaned all the internals of your carburetors really good.. only to discover, often times, your motorcycle will run decent, again, for a short time, before your carburetor problems start, all over, again, invisible dirty fuel delivery system.