Broken idle tube

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Ringer
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Broken idle tube

Postby Ringer » Tue Jul 27, 2021 7:08 pm

While rebuilding the carbureter on my 1950 cub, I managed to twist off the idle tube despite being extra careful not do that. I feel like an idiot. It is an IH carburetor. My question is, what is the best way to fix this?

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Re: Broken idle tube

Postby tst » Tue Jul 27, 2021 8:28 pm

new tube and a 4-48 tap

Ringer
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Re: Broken idle tube

Postby Ringer » Tue Jul 27, 2021 9:15 pm

I tried measuring the thread pitch of my new tube. The finest thread pitch gauge I had was a 40 and it wasnt lining up. So 4-48 must be right. Thanks for the reply

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Re: Broken idle tube

Postby Bob McCarty » Tue Jul 27, 2021 9:19 pm

Spray it with a good penetrating oil for a day or two. If you have any small left hand drill bits, you can use them with a large handled pin vise, don't use an electric drill. McDonald Carb sells the idle tubes for the least cost.
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Stanton
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Re: Broken idle tube

Postby Stanton » Wed Jul 28, 2021 6:03 am

A 50/50 mix of acetone and ATF works well as a penetrant. If you don't have left-hand bits, that's ok. Just measure your new tube threaded portion and mark your drill bit that deep (or less) so you don't go in too far. Go slow. Pick out all the pieces and re-tap the hole. Should be fine.

Where did you get your new tube from?

Don't feel bad. A lot of people have broke that tube off.
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Ringer
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Re: Broken idle tube

Postby Ringer » Wed Jul 28, 2021 6:56 am

I purchased a rebuild kit from famallcubforever. I let it soak overnight in penetrating oil. I'll see if I can find a left handed drill bit today.

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Don McCombs
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Re: Broken idle tube

Postby Don McCombs » Wed Jul 28, 2021 8:12 am

Harbor Freight has them, if there’s one near you.
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Re: Broken idle tube

Postby NJ Farmer » Wed Jul 28, 2021 8:45 am

The good news is the idle tube is brass (nice and soft) the bad news is the carburetor material is aluminum (slightly harder than soft) so be careful and NO POWER TOOLS. I’ve don’t several tube replacements and they are not too bad to replace.

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Denny Clayton
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Re: Broken idle tube

Postby Denny Clayton » Wed Jul 28, 2021 9:21 am

Ringer wrote:I purchased a rebuild kit from famallcubforever. I let it soak overnight in penetrating oil. I'll see if I can find a left handed drill bit today.

You need a 3/32" LH drill bit. I got mine at NAPA several years ago.
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Ringer
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Re: Broken idle tube

Postby Ringer » Wed Jul 28, 2021 11:38 am

I picked up a 3/32 l/h drill bit but had to order the 4-48 tap. Should be in Friday. I'll let her soak until then.

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Re: Broken idle tube

Postby Jim Becker » Wed Jul 28, 2021 1:22 pm

With a little luck, you may not need the tap. It depends on how stuck the stub is.

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Re: Broken idle tube

Postby Clemsonfor » Fri Jul 30, 2021 8:01 pm

:{_}: Well it's Friday!! :{_}: :D :lol:

Ringer
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Re: Broken idle tube

Postby Ringer » Sun Aug 01, 2021 8:35 am

Tap hasnt arrived yet. Now I'm told it'll be here monday.

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Re: Broken idle tube

Postby Ringer » Mon Aug 02, 2021 3:21 pm

Update. I was able to get the broken off piece out of the idle tube out of the carb with the left handed drill bit. I chased the threads with the new tap and the new idle tube went right in. I mated both halves of the carb and verified it was inserted deep enough. All is well. Thanks for everyones help.

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indy61
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Re: Broken idle tube

Postby indy61 » Mon Aug 02, 2021 3:37 pm

I'm not sure what the idle tube does but my Cub ran fine without one. I decided to rebuild mine when I noticed the top was warped and it had a broken/missing idle tube. Ran fine at idle or full throttle?


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