Farmall Cub

My 1970 IH Cub arrived to it's new home for the first time last Saturday eve. With realatively low hours for it's age, and having been well cared for, this Cub showed no signs of mechanical problems before bringing it home. Other than starting it up to unload and move under the barn, it sat all week until yesterday before I ran it again. It started instantly and I drove it down the road a little ways, then back to the barn since it was very low on gas. I parked it, and shut off the engine. Added about a half tank of gas, and then the trouble started. I noted at that point that the carb was leaking a steady drop every second or so. I tried to start the engine and it would not hit a lick. I turned off the gas and the carb continued to leak. I went back and forth for about 10 or 15 minutes trying to start the engine and get the gas to stop leaking out. Eventually the carb stopped leaking gas on it's own. After that, I was able to start the engine. Next, I drove the Cub around another 15 minutes and returned it to the barn. Since then, I've noted no further leaking from the carb.

Q1. Any ideas what happend and how should I address it?
Q2. How many revolutions should I turn the gas cut-off valve when opening it up for normal operation?

Thanks, Harv

Where was carb leaking? Open the valve all the way(till it stops turning)

Since the tractor was almost out of gas you probably stirred up some dirt that was in the tank when you added more gas. Then some dirt may have got stuck and wouldn't let the needle valve close all the way which would have caused the tractor to flood and gas to drip out.

I normally just turn the fuel valve all the way until it won't turn anymore to open and close it.

Your 1970 Cub is in need of some 2012 maintenance. 42 years of crud and rust in the tank will continue to cause you a headache like you just experienced.

I would highly suggest starting at the top by draining and flushing the fuel tank to remove the foreign objects. Depending on the condition of the inside of the tank, it may need sealed.

Continue down to the fuel sediment bowl and strainer screen, throw away any previously owner added inline fuel filters, and finish the job off with a carb rebuild kit after thoroughly cleaning the carb and inlet screen.

With the above tasks accomplished, you should have another 42 years of trouble free service.

A word of advice would be to work on only one engine component system at a time to prevent double system failure. For example, don't replace the plug wires while you re-do the fuel system because if you can't get the tractor started, you will not know if it is s fuel problem or a mixed up plug wire problem.

Good luck!

tmays wrote:Where was carb leaking? Open the valve all the way(till it stops turning)

Like Thomas said, open the sediment bowl all of the way as most of them are back seated meaning they may leak from the stem if not opened fully.

Also, if your carburetor is adjusted properly and all components are functioning, the carburetor should not leak at all---regardless of whether or not the sediment bowl valve is open or closed. I would focus on your carburetor in this instance as others have said.

Even with the carb needle valve working correctly, I've seen seepage from the carb bowl gasket. They are about $5 at the dealer and can be swapped on the tractor.

I only open the gas valve 1/2 turn on both of my cubs. Never had any leakage past the stem and really easy to tell if the gas is on or off.....

ntrenn wrote:Even with the carb needle valve working correctly, I've seen seepage from the carb bowl gasket. They are about $5 at the dealer and can be swapped on the tractor.

The float level height should maybe be checked then as a possible cause. Carb body warpage could be a result also. With all components adjusted and in good working order, the carburetor should not leak.

ntrenn wrote:I only open the gas valve 1/2 turn on both of my cubs. Never had any leakage past the stem and really easy to tell if the gas is on or off.....

Not all sediment bowl valves were backseated, so if you have one that is not, in that case it would not leak as you mentioned.

most likely trash under the needle valve in the carb, clean the bowl and screen install new rubber gasket and dont mess with the carb other than taking the jet out on the sideof the carb [3/8 wrench] and let some gas run through it after cleaning the bowl. Most likely that will solve the problem unless it leaks again. Then remove and rebuild the carb.

Boss

Be very careful not to break off the idle tube, don't ask how I know, LOL.

Thanks to all of you folks for your comments and advice. I was out of town until today and just got to reading the threads. Regarding the suggestions of cleaning out the carb (bowl, screen, replace rubber gasket), is there a thread I can read to see which portions of the carb I disasemble to do this? The gas tank is very clean and rust free inside it, should I be seeing any sediment in the glass bowl otherwise?

This How To article should be helpful -- Lurker Carl's Cub Carb Fixes.

For the IH 3/4" Updraft here is the parts breakdown.



If you have a Zenith then here is the parts breakdown.

284wahoo wrote: Regarding the suggestions of cleaning out the carb (bowl, screen, replace rubber gasket), is there a thread I can read to see which portions of the carb I disasemble to do this?

I believe that Boss Hog was talking about cleaning the bowl and screen and replacing the gasket for the sediment bowl (located under the gas tank).

284wahoo wrote: is there a thread I can read to see which portions of the carb I disasemble to do this?

Which is why I posted the two pages and the link ...

Cleaning the sediment bowl assembly is a different thing entirely.

284wahoo wrote:The gas tank is very clean and rust free inside it, should I be seeing any sediment in the glass bowl otherwise?

If the gas tank is clean as a whistle then no, but real life isn't usually that easy. You may see stuff in the bowl, but that is what the sediment bowl is for - to collect sediment and crud and keep it out of the carb.