I have never worked on a CB-1, but typically gas pouring out of motorcycle carbs is caused by the float valve needles having rust under them or sticky varnish from dried out gas coating the bore the needles go into. Take the float bowls off, the float valve needles out and scrub the bores with qtips wetted with carburetor cleaner until they are clean. That fixed my CB700SC and CB900F. Check the tip of the needle valve also. If there is any trace of a groove where it seats in the carb body it will probably still leak.