Hi, With modern petrol containing ethanol, and water dissolved in the ethanol, you will need bigger main jet sizes than those you quote, ie. 190 and 200 for starters. This by no means written in stone as they are all different, but worth a try once you have sorted out ignition/timing issues. If your carb is as worn as you suggest, fitting a new slide may not cure it as it probably needs a rebore and oversize slide. Martyn Bratby has done several for me in the past, and I have always been pleased with the results.