One possible cause for misting out of the carburetor would be if the fluid level within the bowl was much too high.
(The float bowl is considered to be a third "circuit", along with the lowspeed and highspeed needles.)
This would occur if the float was too heavy, either by soaking up fuel ("logging"), or being made of an inappropriate material such as brass or certain modern nitrophyl replacements. The float may also have swollen due to digestive modern fuels, and be hanging up upon the bowlstem or side of the bowl.
Note also, that even with a top-quality float, the bowl should be rotated so that valve is as close to the choke mechanism as possible. (L&L's blueprint for the M741 shows 15/64" from the bowl to the aircleaner flange, in addition to the offset shown in most manuals.)
Let us know what you find,
PS: It is prudent to never start a machine without the aircleaner, as it is a "spark arrestor", and a fire can easily occur.