As per my little experience asif shah is not that reliable, I had an HJ60 and I took it to him and all he could figure out was to put half liter lube oil in every tank of diesel.
Than I discussed it with a friend who deals in generators and he sent me to his reliable diesel mechanic on band road near saggian bridge, and he found out that its was worn out diesel pump diaphragm and new one was only for Rs. 1500 and pick increased about 30%.
His contact no is Bilal 0300-4414588