yea,what carb do you have. And we can only give you a range to work on,its up to you to get the jetting perfect, jetting doesnt mean jsut changing the main jet, needle clip needs to be changed sometimes and pilot jet.
a stock carb on a 240......ugh....that 240 is crying for more fuel and air but anyway i would try around a 300 to 350 mabe....and plug chop to see what its doing