Motorcycle Repair: gas leak from carb, carb, float valve

Question
My son has a 2003 Honda XR70R, it is leaking gas from the drain hose coming out of the bottom of the carb. It is flowing at a steady rate, any idea what could cause this?
                                Thank You

Answer
Fuel coming out of the overflow tube is usually caused by the float valve in the carb not shutting properly. This can be caused by a defective or damaged float, but it is more often the result of debris that has made it's way from the fuel tank and prevents the needle from contacting the seat properly.

To clear the float valve:
- Shut off the fuel if your petcock has an off position. If you have a vacuum operated petcock with no "off" don't worry - fuel can only flow when the engine is running and producing vacuum to open the valve.
- Remove the float bowl. This can usually be done without removing the carb. A service manual would help you figure out how many screws there are and where they are.
- Remove the float. This is usually accomplished by either pushing or pulling out the float's hinge pin. Be careful not to loose the needle when the float comes out.
- When the needle comes out of the seat the debris will usually fall out (or be flushed out by any fuel left in the system), but if you want to make sure you can clean the seat with a cotton swab dipped in carb cleaner or methanol.
- Before reassembling the carb take a good look at the float. If it has fuel inside it or has an obvious defect, replace it. As I said before, a blocked float valve is more likely.