I just bought an 86 moto4 250. When i turn the fuel switch to on or to reserve it pours fuel out the carburetor drain tube????? why does it do this????

 

the float bowl drain? i'd say the screw is open or some debris is in it keeping it from sealing the drain. if you're talking about a different tube than what i'm thinking of, the float/needle valve could be stuck open.

 

i believe it is the float bowl drain, how can i fix it

 

bottom of the float bowl, where the hose connects, is there a "screw"? if so, unscrew it a ways, let the gasoline flow, then retighten it. there may be debris in the seat of the screw. if that doesn't do it, isolate the fuel tank from the carb, take the carb off or just remove the float bowl. if i was you, seeing how it sounds like this quad has sat for a while, go ahead and remove the carb and give it a good cleaning. jets also, then we can get all of the debris, solids, and varnish gunk out of the carb. in case you don't know how to clean a carb or its jets, here's a hyperlink or two to help guide you.

how to clean a carb on a ATV - YouTube

How to clean a carburetor in 15 minutes - YouTube

your carb may not be identical, but it's the principle of the exercise. all carbs have to be cleaned sooner or later and most are done the same way.