Wed Jul 24, 2013 7:20 pm
Eugene wrote:Check needle valve and seat and gasket for fuel leak.
Some place on this board is photos and a description of bench testing carburetors for leaks and fuel level.
Edit: Search "bench test carburetor" on this site. 11 hits.
Fri Jul 26, 2013 9:02 am
Arnold wrote:The visible leak is inside the air intake chamber from a port in the cylinder wall above and behind the shutter assembly.
Do you mean the choke? I do not have a carb in front of me but I can't think of a port behind or down stream of the choke. There is a port upstream that goes to the bowl, if the the bowl overflows then it can leak out of that hole.
Fri Jul 26, 2013 10:06 am
I might be way off on this, but if you bought a NEW carburetor wouldn't it be a Zenith carburetor? I know you called it an IH carb, but does that mean that it says IH on the bowl, or that you got it from the dealership? Just thought that this might be the source of some confusion.
Fri Jul 26, 2013 10:29 am
Some aftermarket suppliers now offer a new carburetor that is much like (identical to?) the original IH unit.
Fri Jul 26, 2013 12:36 pm
IH 3/4" Updraft Carb
New Reproduction Carb IHS738 at Steiner Tractor
Fri Jul 26, 2013 8:15 pm
Bus Driver wrote:Some aftermarket suppliers now offer a new carburetor that is much like (identical to?) the original IH unit.
Not quite identical, but a good carburetor...viewtopic.php?f=139&t=20230
Fri Jul 26, 2013 9:53 pm
I'll answer the latest questions.
Don - Yes I mean the choke. I called it the shutter assembly as is written on the schematic seen in earlier post. The port is above and to the left as you look in from the air intake. Fuel drips down almost invisibly but fills the cylindrical air intake about 1/4 high so that when the rubber hose is taken off it is like a waterfall.
Glenhuff - It is not a Zenith. I checked with Hoober Case/IH and with the invoice numbers it is an IH remanufactured carb. It has no markings on it at all.
Bus driver - Yes it is identical to the original as IH told me.
Rudi - Your photograph is it.
Don - The post you wrote and photos reviewing the carb describes mine. The photo of the needle and notched seat are the same. I've looked in the carb with a magnifying glass and have been impressed at how smooth the metal is.
I had to put things away for a few days but will go through bench tests tomorrow.
Sat Jul 27, 2013 8:52 pm
I carefully pulled apart the carburetor and inspected the halves' cork gasket that came with the kit. It was put on and off several times and developed a few tears. The gasket screw hole at the fuel bowl side does not line up correctly pushing the cork inwards toward bowl. Also along this edge there is a bit of an inward curve of extra gasket material. It seems as if the fuel causes the cork to swell. When the gasket was original and later dried from dis-assembly the inward curve was clear by measurement and clear by hearing the bowl rattle inside. When reassembled it seems that the cork swells enough to eventually impair the float movement. I reinstalled the original black thin gasket (see Don' photo) and have had no leaking.
It seems the solution was to replace the needle valve gasket and discharge nozzle gasket with new gaskets covered in Permatex 2 sealant. The cork gasket should either be trimmed on the inside bowl side, redrill the bowl side hole, or not use it at all.
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Last edited by Arnold on Sun Jul 28, 2013 6:36 pm, edited 1 time in total.
Sat Jul 27, 2013 9:16 pm
"the cork swells enough to eventually impair the bowl movement" Do you mean the float movement?
Give us a report early next week on the (hopefully) success of the latest effort.
If necessary to hold gaskets in place, auto weatherstrip cement can be used on the bowl gasket surfaces. I well remember when Goodyear introduced PlioBond , which is similar to the weatherstrip cement, about the time of the Korean War.
Sat Jul 27, 2013 9:24 pm
What is the source of the gasket shown in your photo? Thanks.
Sun Jul 28, 2013 6:47 pm
Thanks Bus driver I edited my post saying it affects float movement.
The photo of cork gasket on TM's website shows a straighter bowl side form. As long as the hole is correctly punched out.
I bought my deformed cork gasket as needle valve kit from Naylor Tractor Parts, Liberty, Ohio. When I called Hoober (finally took four weeks) and other suppliers in early June no one had a kit in stock except Naylor.
When I later contacted Hoober Case/IH for their needle valve kit they said the 'all steel needle' is not made anymore, only rubber tipped are available.
Sun Jul 28, 2013 6:56 pm
Obviously the parts guy at Hoober ain't exactly up to snuff on his parts now is he?
That is one of the reasons why TM Tractor is a good place to get parts. Usually out that day or next .. be surprised at how fast it gets delivered. Blows me away when they ship me stuff up here -- faster than local dealers could hope to be.
Tue Aug 06, 2013 12:56 pm
Update: I used the tractor a few times during the week and all week left the fuel cock full open to see how my carburetor fixes would react. There were no leaks. I reused the original thin black gasket for the halves and it became waterlogged with fuel and fuel seeps out slightly. I will put in a cork gasket from TM. And when not using the cub I will close the fuel cock and run the engine draining the carb.
Wed Aug 07, 2013 7:22 am
Shutting off the fuel and running the carburetor dry is a good practice -- but not so convenient. Some of the early John Deere tractors used that as the standard shut-down procedure.
With battery ignition, it is easy to forget to shut off the ignition after the engine stops. The consequences of that can be significant.
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