Motorcycle Repair: 1980 honda cb900c, slide check, family memeber

Question
i recently was giving a 1980 honda cb900c from a family memeber. it was her husbands and he recently past away so she had no use for it and gave it to me. well i got it it was assembled except the gas tank wasnt secure seat was off, frel lines were disconected. i took out the carbs and cleaned them and reinstalled and reran the fuel lines. i went to start it and it wouldnt. i discovered i wasnt getting vaccum to the diaphram i tried my best to seal the vaccum line up and with a little pump from the vacuum pump to fill the carbs it will start and run from 3 minutes to 9 mostly around five minutes then it dies out and then its hard to start for like 10 mins then sometimes when i start it, it kicks up like the throtle is wide open i need some help here to get it back in shape in time for a christmas present for my fiance's father. any ideas? would using a battery charger as the main power source affect it. the battery holds a little charge but i dont want to buy anything until im sure it will run thanks for any ideas

Answer
Dan,

-check for a sticky carb slide.
-check if all the pipes are warming up.
-check the fuel petcock valve diaphragm for holes.
-check for spark and if okay, spray wd40
in the carb mouth to see if it fires.
If it does then you know you have a lack of fuel
for some reason. Check tank, petcock and lines.
-a battery may help as the ignitions are designed
to protect themselves from low voltages.