@kennygoh016, welcome here!
Banging and explosions from your mufflers side usually means a too lean gas/ air ratio.
Could be a choked airfilter or your carb too lean regulated. Best way to find out would be an emission test in a workshop.
I would start to check airfilter and airways towards carb. Sometimes KYMCOs suck gearoil into its filter.
There is a transparent hose with a plug down under your motor, called "puke pipe" this has to be emptied regularely from oil/ water residues.