i did have the tank cleaned
i had a radiator shop clean the tank, then i tore down the petcock and cleaned it all up and the filters. then i took the carb apart and removed the floats, jets. cleaned out all the rust from them. then i used carb cleaner and sprayed out the rest of the parts that i could get to. at that point i put it all back together without replacing any of the o-rings, floats, jets...
when i got it all back together, plugged in the fuel and vacuum lines, put in some clean fuel. i cranked it till it started. it idles just fine then about 2-3 minutes into idling it died. started it right back up and tried to open up the throttle and it died immediately. kept messing with it but no matter what it always dies. went back to letting it idle to make sure that the vacuum lines were pulling air. i then checked the drain screws on the carb to make sure that plenty of fuel was comming out. i built one of the home made mamometers to make sure that both side of the vacuum was pulling correctly. it is off with one side pulling about 1/2 inch more vacuum. i figure that is pretty close. (may be wrong about it being close enough) i figure that maybe by opening up the carb and spraying carb cleaner in it i might have mess up one or more of the seals but supposedly that stuff is ok to use. (maybe not).
so that is why i want to see about putting in new o-rings and maybe other parts. its the other parts that i am concerned with.