[drysumpjet]

In my case, I had to drill out the main jet to obtain adjustment, utilizing drill bits from a numbered (not to be confused with fractional) drill set. I can't rememember the drill size, but it ended up 2 sizes larger than the stock jet.

The carbuator was from new old stock, 1" bore #30, I'm not sure if the main jet was sized specifically for a 14HP or 16HP or if it's the same for both motors. Surely others may be able to chime in on that.

Also note, in my case, the motor has been "ported" and has valve reliefs machined into the combustion area of the block.

Interesting note, due to the configuation of the fuel ports in this carb, if the high speed mixture adjustment needle is screwed out more than approx 4 turns, it plays HAVOC with the idle circuit fuel feed!
What happens is the upper threaded body portion of the adjustment screw blocks the idle circuit fuel feed port. (Observe the idle fuel passage starts at the top of the high speed mixture adjustment screw)
Suspect symtoms of this condition is the idle being too "lean" where-as screwing the idle mixure adjustment screw out further has little/no effect on the idle quality.

A larger main jet allowed for the high speed mixture adjustment screw to be adjusted "in" further, which took care of my issue.

As always, "Your Results May Vary!"