PerumalSamy

I am using SZR150CC bike. It makes wired knocking sound in silencer and motor cycle jerks too and fro suddenly while in motion irrespective of which gear i am on. I done service at Yamaha service station. Again it remains the same. They changed spark plugs, checked carburetor and adjusted idle RPM etc. I can not find where the exact problem is... Please help me to get rid of. I am getting a mileage of 35 km/Lit. what are all the suitable ways to improve mileage?. please give some suggestions to improve mileage in technical aspects.