the mixture screw doesnt alter by itself so there is another problem,dont touch the mixture screw they are preset at the factory by dellorto and do not need adjusting unless someone has messed about with it already they are set 2.5 turns out from being in all the way.If like your saying its hard to start and cuts out when you try to rev it then the engine is running weak i suspect the carb may have water in it or possible one of the reed valve petals has a crack or split in it also the main or pilot jet in the carb may be blocked or a crankseal leaking will cause this too as will a leaking airbox or link hose to the carb.just this week i have worked on an aerox 50 that would only idle and when you tried to open the throttle it died,i suspected the reed petal was broken and it was, i replaced it with a new carbon set from v-e uk and it ran like new afterwards,of course as i have said its not the only possible cause .
adam bike doctor, January 2010
