Kaufberatung GS 500E !help! at test drive she hardly started

Hi, I have to buy a GS 500 E for daily use. I have made myself smart on the internet and found a lot of used ones. Just now I come back from a visit. Built 1994 – 28000 km – 4th hand – black – new tires + chain. Defects it has only slight scratches on the tank of ner pants – on the exhaust bigger scratches, possibly from a slide. just the same front of the “motor bar” left + right. Otherwise it looks really top in shot. AAAABER: As the older one e Lord wanted to turn on the part, she didn’t go on. eternally gurgled – NIX! then we checked if the gas tap was right. I don’t remember how it stood. Anyway we switched to “reserve” – I thought it’s safe – because I wasn’t sure if down or up ^^ again – NIX! then we put the tap down – after longer gurgling she came then! however if you wanted to turn up for a short while, she went out. – and then she ran without problems! IS THE NORMAL? or was that because of the cock’s stint? or can you not turn it on with reserve? please for help ^^ THANK YOU already