Need advice please. Due to budget constraints we bought a MAC AFRIC 6.5 kVA (5 KW) Generator (with T.F.V meter). We ran it previously for 2 hours on petrol without issues. We then had a soundbox and exhaust installed. Last night we ran it on LPG, it went for about 15 min then cut out. This morning i cleaned everything, installed new gaskets on carb, changed sparkplug and air filter and topped up oil. Started it, ran for 5 min backfired and cut out. Gasline from bottle is not kinked or damaged and choke was in half open position. Any ideas what could be the cause?