first thing is that ur bike is giving normal avg at this speed in my opinion ..
if u want to get max avg .. they try running it b/w 34-45 km/hr max .. dont go above it .. u will surely get awesome avg ..
jets is something that are rarely changed/replaced .. so very few shopkeepers keep it ...
and just ask ur mechanic what is the main jet number of my carb when he opens it .. google for pz16 or pz22 .. and see the images to have an idea where is main jet located .. at high speed its responsible for petrol consumption .. i.e. it controls amount of petrol at high speeds .. every bike has its specific jet numbers .. replace with exactly same sized jet .. same number .. jets are labelled... and dont leave ur old jet at shopekeeper .. keep it safe with u . in case new jets are not satisfactory u can have them handy ..
pilot jet should be 35 .. but do verify it ..
once again .. at the speed mentioned that avg is quite normal .. though not as normal but still its ok ..
ride it in economy range .. if u want economy ..
else dont expect economy in speed range ..