IH Cub carb throttle body expansion plug

[staninlowerAL]

What's underneath this plug (ref. #5) IH Part #37 417 D? Anyone ever removed or replaced it? Some IH carbs have it and some don't. Thanks, Stan

[CharlieK]

fuzzy pic

[Stoffregen Motorsports]

I've never had that plug out of a IH carb, but I would assume it's leftover from when the carb was machined. Instead of drilling a blind hole, they drilled through the carb body (for the idle mixture jet?) and this plug is the other end of the orifice.

[Bob McCarty]

Stan, I have a broken top and went ahead and drilled out the brass plug. It is about 1/4" in length. A wire run through it can be seen in the hole where the air adjustment screw goes and it connects to the idle tube. The two small holes in the carb throat also enter that "tube". What are you trying to remove on your carb that you think might be accessible through the hole the brass plug is in?

[staninlowerAL]

Thanks Bob. Sorry for the delay, dealing with life issues today. I was hoping to be able to see the upper end of the idle tube jet below the plug. I'm a little uncomfortable about drilling blind from the bottom. I picked up a pin vise today, maybe that will make it a little easier when I get the correct tap. Do you know the length of the tube that is extending from the top after it is seated in the threads? If I knew that measurement I would know how much of the tube is in the carb top. I do have a new replacement jet from Morgan McDonald. Thanks.

[staninlowerAL]

Update: I got the threads cleaned out and the replacement idle tube jet screwed into the upper half of the carb. Time now to reassemble everything and give it a run test. Thanks for the suggestions and comments from everyone and especially to Bob McCarty and Don McCombs who gave special help via PM, email and phone calls . Stan

[Don McCombs]

Good luck with the test flight, Stan.

[staninlowerAL]

Thanks, Don.