There are no adjustments on the Solex carburetor. The most interesting thing about the Solex carb is that there is no float bowl. Any unused fuel at the carb gets sent back to the fuel tank. Cleanliness is very important. The orifices are tiny and the smallest piece of dirt or whatever can clog the passageways. Sometimes the jet gets a little restricted/clogged and needs to be removed and blown through to clear it. Never use a piece of wire to clean the jet as you can scrape the inside the smallest amount and change it's characteristics.