No diagrams take the pot / bottom off the carby and in the middle is a brass round thing with a hole in the middle most have a line cut in them for a flat head screw driver or their like a nut thats the jet hole so you make it biger or smaller. Have you got a stock carby or hp one the stock one has a adjustable needle / clip. A bigger gap on the plug will fire when there is lots of petrol. I run the most petrol sittings on stock carby and a big gap good oil to petrol and all ways get 60kph or over