I have been playing around with a couple of different carbs. (WYL,WYJ) and these do not have adjustable needles. There are various jets fixed in these carbs and I have noticed a size difference in what is called the "fuel inlet needle". My question is, even though it is possible to replace the main jet with a bigger one or drill it out, will the "inlet needle" prevent running the carb rich since it restricts the flow of fuel to the carb.? Common sense tells me it should but I would like to hear from those who are way more knowledgable then I on this subject. I am asking this because others are unable to see a performance increase or get the engine to run rich after increasing the main jet size. I am working on converting a Briggs & Straton 40cc, four stroke and hope to find a good carb solution. Thanks for your consideration.