This has happened to me intermittently in the past, but I cannot find a common cause. I have used the snowblower for almost 10 yrs now, and put a new carb on it when I got it because it was doing the same thing. I've taken the float bowl off, checked the needle to make sure it wasn't sticking, sprayed the carb internally with carb cleaner, and it STILL starts flooding out the top (vent hole?) after a few seconds of running.
Is there a rebuild kit for this carb that would replace anything that would be causing this? Should I just get another new carb?