So I just got this 1980 xs1100 special and so far I love it but have yet to get it started. I just replaced the carbs but it is backfiring consistantly. On the plug above the carbs with the 4 inlets for the fuel and one vaccum line on the other side. Where does it attach to? I am assuming that, that is the reason why it is back firing because there is a lack of vaccum. Please help me out here I really want to get this bike going before the winter. Thanx