How important is the idle tube?

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How important is the idle tube?

Postby jrob69 » Wed May 15, 2013 6:07 am

With the carb apart on our 48 cub, you can see the idle tube is stuck with about a 1/8" of the tube sticking up above the bottom part of the carb. It looks to be broken off where the thread starts. How does this effect the how the tractor runs or idles?
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Re: How important is the idle tube?

Postby Bezirk » Wed May 15, 2013 6:18 am

It does have an effect on the performance of the engine, however on my first Cub the tube was broken and missing from the carb. The engine ran and at Boss Hogs fest I learned that it was supposed to be there. I got more info from the guys at the fest and Bob from Ct. went to his car brought me a tube and would not accept payment. Ths was my first lesson about the generosity of the good people at the Fest. I drilled out the old tube rethreaded the hole inserted the new tube and it has run fine for several years now.
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Re: How important is the idle tube?

Postby Tezell » Wed May 15, 2013 6:54 am

I have 2 or 3 that is broken off and honestly I cannot tell which ones it is without opening the carbs. I am sure it makes a difference. I just do not know how much.
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Re: How important is the idle tube?

Postby bob in CT » Wed May 15, 2013 7:05 am

Bezirk wrote:It does have an effect on the performance of the engine, however on my first Cub the tube was broken and missing from the carb. The engine ran and at Boss Hogs fest I learned that it was supposed to be there. I got more info from the guys at the fest and Bob from Ct. went to his car brought me a tube and would not accept payment. Ths was my first lesson about the generosity of the good people at the Fest. I drilled out the old tube rethreaded the hole inserted the new tube and it has run fine for several years now.
Berlin

Berlin, I don't think that was me but I'll gladly accept payment for it now. :lol:

Idle tubes are not too bad to replace. Many, like one of mine, were broken by neophytes that did not expect them to be there when splitting a carb for the first time. You can buy one for about $15 from Macdonald carb & ignition. It you need a tap, it is a 4-48 thread, not the more common 4-40. A left twist drill is the cat's meow for extracting broken parts. The 4-48 tap drill is #42 so I would use something smaller that that (higher number) as an extractor and you may not need to re-tap at all.
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Re: How important is the idle tube?

Postby RaymondDurban » Wed May 15, 2013 7:55 am

jrob69 wrote:.... How does this effect the how the tractor runs or idles?

As the fellas said above, the tractor will run with the tube broken, but I believe you'll have a hard time getting the RPMs down to low idle specs with it broken.
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Re: How important is the idle tube?

Postby Bezirk » Wed May 15, 2013 5:43 pm

Bob , I hope you dont't charge me interest, if so I'll need to bring a Brink's truck to Cecil's to settle with you ! :lol:
I'll see you at the NE Fest.
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