Without measuring its hard to tell. check the jet size, as .036 stock jet for gas. .050 jet for alchy. check the dia. of the cat eyes, small hole if a #71 drill bit using the shank end will go its an alchy carb. Large hole check with a #.053 drill bit. alchy carb. Turn the screw in by hand until it stops and turn out 1 1/2 turns. Check the jet size. Most jets have the size on them.Jet size is not stamped on the adjustment screw, but on the jet itself. Therefore you have to remove the jet to be able to find the size. By brass screw, I hope you mean the jet. If so, clean it real good some times they are to read. A standard gas jet will stamped .036 or maybe .039. and most are either stamped on the top (slot end) or on the side. After you remove the screw, nut and oring and gasket. the next item is the jet. Well I am not going to state that no number is a rarity, but it is highly unusual. Do you know anyone with a number drill bit set? If so see if they can check the size. That will be your only way of knowing the jet size.
Sounds like a plan. No dots but I've got milk.
bummer..i dont have the tool to measure something so small, and dont have tiny drill bits.
