Farmall Cub

The cub I just purchased needed a carb rebuild (according to the previous owner) as it wouldn't idle. He hadn't tackled that sub-project before his heart attack slowed him down.

No problem, sez I, I'll read up on the IH carb and git-r-done. So I read every thing I could find on the subject - most of it located on this site and very comprehensive. When I pulled it apart, the first thing I noticed was the broken & missing idle tube. Aha! Very Common. But what puzzled me was the lack of a main jet... I mean it wasn't there... no hole in the bowl for one, either. Temporarily skipping that, I stripped everything down and after an overnight solvent bath and two hours in the heated ultrasonic tank I noticed a faint impression of where the main jet SHOULD have passed through the outer wall of the bowl. As it turns out, someone, years ago, had broken off the main jet at the end of the threads. Noticing that fuel would leak from the outside hole in the bowl, they plugged it by hammering in what appears to be lead fishing sinkers and dressing the outside flush! However, it did work and it didn't leak, so I guess I can't argue with the utility of the repair. LOL! After drilling out the main jet and re-tapping I resurfaced the area where the main jet gasket contacts the outside of the bowl.

Also noticed the upper housing was warped from overtightening. Having seen references to several plates online here I made my own. It works very well.





Flipped the plate upside down and used it as a jig to hold the upper housing square while I drilled out the broken idle tube.



Now we wait until my rebuild kit arrives from Steiner...

if you ever decide to make more of the carb jigs put me down for one

Rob in NH wrote:if you ever decide to make more of the carb jigs put me down for one

Me too...how much????

Is the main jet broken off inside? It goes through the housing, where you found the lead patch, and threads in further inside. I doubt it would have run, without that end. (the actual jet portion) Ed

Nothing like solving a mystery!

Sweet jig! The carb turned out real nice!

Because you did all that reading I am sure you noticed that the idle tube is a somewhat uncommon 4- 48 thread.
It looks like a nice clean job you did. When I saw your tools and the can of cutting oil I expected it to be so.

Tractorboy3 wrote:

Rob in NH wrote:if you ever decide to make more of the carb jigs put me down for one

Me too...how much????

Add me to the list

John:

Nicely done I am impressed with your jig. Nicely done If you have a measured drawing it would be a nice addition to the server, the CBoK and the How To Forum. Interesting use of the jig to drill and re-tap the idle tube

Rob in NH wrote:if you ever decide to make more of the carb jigs put me down for one

I hadn't intended making these for sale, but will look into it.

I'd like a jig too. Please put me down on the list

ScottyD'sdad wrote:Is the main jet broken off inside? It goes through the housing, where you found the lead patch, and threads in further inside. I doubt it would have run, without that end. (the actual jet portion) Ed

That's true. What I was trying to describe is that at first glance, there was no main jet, or place for one - when in actuality, it had broken off inside right at the end of the threads. This left the threaded portion (and orifice) stuck inside.

beaconlight wrote:Because you did all that reading I am sure you noticed that the idle tube is a somewhat uncommon 4- 48 thread.
It looks like a nice clean job you did. When I saw your tools and the can of cutting oil I expected it to be so.

Thanks, I did note that while researching. Thought I had that one, but ended up ordering a set after I discovered the ones I had were 6-48, not 4-48.

Rudi wrote:John:

Nicely done I am impressed with your jig. Nicely done If you have a measured drawing it would be a nice addition to the server, the CBoK and the How To Forum. Interesting use of the jig to drill and re-tap the idle tube

Thanks, Rudi! I worked off a simple sketch. Will clean it up and develop an AutoCad version for the site - that's the least I can do for everything I've learned from you guys.

I love it when a guy says "git-r-done," then whips out a Bridgeport, a can of Tap Magic, and Autocad

My idea of git-r-done is an oxy-acetylene torch, a 2lb cross-pein hammer and a roll of duct tape