It's possible if you have a carburetor with a float that it's either stuck open or damaged.
if your looking down on the petcock from the top of the radiator turn the petcock to the right to loosen it and to the left to tighten.
To drain the gas on a Yamaha TTR 125, start by locating the fuel petcock, usually found on the bottom of the fuel tank. Turn the petcock to the "OFF" position, then disconnect the fuel line from the carburetor and place it in a container to catch the fuel. You can also remove the carburetor drain screw, allowing any remaining fuel to flow out. Make sure to handle the fuel safely and dispose of it properly.
The petcock requires the vacuum of a running engine to stay open. Because you ran the carbs dry you now need to bypass the vacuum system to allow the carbs to fill. Turn the petcock to prime (PRI) and leave for about 30 sec. If it starts, move petcock to on.
FACING the petcock, turn it CLOCKWISE, as if you are screwing it IN. Many times it is a little rusted and hard to turn. Before you start, spray it with any number of products available for rusted or stuck threads, such as WD-40. Then use pliers to gently turn the petcock to the RIGHT. GOOD LUCK!
Float may be stuck in carburetor, or you may need to turn the petcock to the off position when not riding (if applicable). ~RC@HD~ ANSWER: Another posibility is that the gas cap is not venting correctly and when the bike sits in the sun, presure builds up in the tank forcing gas out of the overflow vent in the carb.
To drain the fuel tank on a Yamaha TTR125, first, ensure the bike is turned off and cool. Locate the fuel petcock (valve) on the side of the tank, turn it to the "OFF" position, and disconnect the fuel line from the carburetor using a wrench. Place a container beneath the tank to catch the fuel, then turn the petcock to the "RES" or "ON" position to allow the fuel to drain completely. Dispose of the fuel properly and ensure no spills occur.
Turn it counter clockwise to open.
First turn off the gas at the petcock. Remove the hose from the petcock and attach your own that is long enough to reach your container.
A petcock is a fuel swich on the petrol tank that can turn the flow of petrol to the engine on and off. It usually has a on, off and sometimes reserve setting.
Replace petcock with a properly sized plug Be sure you turned the petcock back in all the way. Try opening and re-closing petcock,may be some trash in it.On mine you have to push in on the petcock and turn it to re-seat it.
Open the radiator petcock by turning in the normal direction, left. See "Related Questions" below for much much more...
To open turn clockwise To totally remove turn body counter-clockwise