last year i did a test that had some how optimal conditions and i think i achieved 63-65kmpl on 78cc dhoom stock engine .. however if situtations were more favourable i could have done 70kmpltr.. as i would drive 1km then take a u turn then again u turn ..
i got i think 6.3km in 100cc fuel .. (fuel was measured using syringe .. so very accurate) and carb was emptied like a thirsty sand in sahara desert .. and the distance measured using gps and google earth .. a patch of 1km almost straight was used .. and i would go from point A to B and back .. and every time i would reach point a or b and i took u turn i would look the fuel level ..
this was when i had replaced its jets with same number jets .