Dear bro!
You're using very heavy engine oil in a new bike.Using 20w-40 in winters is like killing your bike.The "jhatka" problem is occurring most probably cuz of heavy engine oil.Your bike is basically choking,Change oil and try to stick with company's recommended 10w-40.
My experience with Zic 10w-40 is simple marvelous.The sound is reduced..Very smooth acceleration,gear shifting became very soft..