carb plug size

stingray64 · Nov 3, 2009

After brush-hogging discovered gas pouring out a hole in the bottom of the carb float bowl. Parts book lists a "plug, w/filler, drip hole" (not pictured) which I presume is what I have managed to loose. Anyone know what size plug this is? Threaded? Gasket? Available from auto stores? Thanks! oh..almost forgot the important stuff... 1955 300 utility, C-169 gas engine.

Dave_from_Texas · Nov 3, 2009

I would guess it is a 1/4". Buy a drain plug like the ones on a radiator. It comes in handy when you are trouble shooting.

rustyfarmall · Nov 3, 2009

that carburetor does have a threaded drain plug, but I don't think that is what you are talking about? The drip hole, which is at the very bottom of the carb, uses a small disc, similar to a freeze plug, except it has a hole drilled in the center of it. There is also a felt filter that goes in the hole before the plug is "staked" into place. Your best hope of finding these two items will be at your local Case-IH dealer.

BUT, if the gasoline was POURING out of that drip hole, you have some serious issues going on with either the carburetor float, the float valve and seat, or both.

Bob · Nov 3, 2009

I think you are looking for the little sintered bronze filter that does in the drip hole, letting "overflowed" gas out and keeping (most) dirt out.

Better get the right part!

The bowl drain is another matter, typically a 1/8" NPT plug.

Bob M · Nov 3, 2009

The drip hole plug is essentially a flat washer press-fitted into the boss at the bottom of the carb. The small felt disc fits inside the boss and is retained by the plug.

If there's gas running out of the opening it means the carb float needle valve is not closing. Could be junk caught on the needle seat (most likely), or a sunken float, the float binding on the side of the carb bowl, etc. You'll need to find and fix the problem before you replace the plug.

OR....you may find the plug is actually still in place. The dripping gas simply means the plug/felt is doing its job draining overflowing fuel from the carb air passage.

Sam#3 · Nov 3, 2009

Since you don't have the original plug be careful.
I wanted to replace the plug in my case because the head was rounded so one day I was at the local farm store and asked the parts guy for a new plug. He said, "Pick up a 1/4" NPT." Wrong!
The original is a fine thread. A 1/4" may be correct for your application but don't try to force the wrong thread.

stingray64 · Nov 3, 2009

thanks guys! I guess I need to look at it with more daylight and see what goes on. Gotta love the time change! Try to get off work early today. John

carb plug size

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