backfire through the carb.

I would look at something that you did recently like "adjust the valves". You might check over that again. Bad wire, fouled plug, timing way too advanced, moisture, it could be a number of things but usually you can trace things back to something that you changed or did differently. In addition, with the collapsed hose you might check your thermostat to see if it`s opening. Good luck, let us know what you find.