If your motorcycle is leaking gas take a close look to see where the leak is originating. Common problems would include a leaky fuel valve (petcock), damaged fuel line, or if the fuel is coming from the carburetor, a stuck float. A leaky fuel valve or damaged fuel line can be replaced, while a stuck carburetor float can typically be fixed. The carburetor may just need some taps on the float bowl with the handle of a screwdriver to free the stuck float. If that doesn't work, make sure the fuel valve is off, remove the float bowl and check for grit or any debris that could be causing the float needle to not completely seat, which would allow gas to continue flowing into the float bowl even when it is full.