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Need help with my farmall cub


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I have had the same intermittent problem with my cub and it showed up again this weekend. I was mowing with it for about an hour and fifteen minutes and it ran perfect. I then started to notice what sounds like a miss every once in a while, about 15 minutes later it was sputtering and running rough. Now it will run pretty good at a low rpm but will run poorly at full throttle. It will run smooth for a few seconds then sputter, then run smooth for a few seconds then sputter.

It has done this before and I have tinkered with different things (new coil, plugwires, electrical wiring) It will run right for a couple weeks and then act up again. The one thing I know that it needs is the generator rebuilt. Could this be the root of my problem? I did charge the battery up good and it is still acting up.

 

Brandon

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it could be the battery is getting weak after a little while and losing good spark if not getting charged and losing voltage, simply check with volt meter on that one, next maybe a condenser getting warm and giving up but not as likely if its acting same as before you replaced, could be a coil getting warm and losing power/juice and weak spark. Could be screen sucking full in bottom of tank or sediment screen and just finally gets enough junk sloshing around in teh tank to suck it full. Those some thoughts to try maybe not worth a hoot but gotta start somewhere. 

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Make sure fuel tank is clean then go to sediment bowl (fuel bowl) tank it out an see if there is junk in the bowl and on the screen. Also check the fuel bowl gasket if it is in good shape. The gasket and screen are right above the fuel bowl when you take it out. 

If that isn’t the issue drain the carb like J-mech said. 

Finally the carb may be rebuilding with a new carb kit ( but do simple stuff like said above before buying). Electrical may be an issue also I’m not sure. 

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It could be vapor locking.   If you shut it off and let it cool down for an hour, does it start & run fine again?

Also, check the vent on the gas cap.  If that gets plugged it can cause poor running after operating for a bit.  Easy to test--loosen the cap!

To test the "Low voltage" idea, hook up a battery charger while its "missing".  If the engine smooths out, that might be the problem.

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Posted (edited)

Thanks for all the suggestion. I am working my way through them. Here is a video for you guys to hear what it is doing

Sorry but the audio does not seem to be working. I will try and fix it later

 

VID-20200406-151505.GIF

Edited by Blee25
Vieo
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Inside your tank where your sediment bowl screws on from bottom , I take a piece of fine brass screen 2" tall and roll up like a cigarette and stick it in the top of your sediment bowl.

Only way i can keep a cub running anymore with rust in tanks. 

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How about a good ol' tune up, points, condenser, plugs champion d21's

 

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18 hours ago, Blee25 said:

 

Here is a shot video for you guys to hear what it is going.

I have tried running with the battery charger on it and it makes no difference. Tried loosening the gas cap. The coil, plugs, and plug wire have been changed and the problem keeps coming back. Has flows from the tank to the carb freely. So I am deducting that the problem in the carb itself? 

Thanks for any suggestions in advanve.

Brandon

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Definitely seems to be starving for fuel

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Every carb problem I've ever seen the tractor doesn't run right all the time, not just after running for a while.

Again, it could be vapor locking.   Fuel flows freely until the tank and line get hot, then fuel begins to vaporize in the line, basically creating a vapor bubble that blocks flow. 

I had a Ford 800 utility that would run great until it warmed up, then begin to spit and sputter, then die.   The fuel line ran thru the exhaust manifold.  After looking at some parts books, I realized that there was supposed to be a heat shield between the fuel tank and the muffler.    Fabricated a shield, and rerouted the fuel line out around the front of the motor and back to the carb.   End of problem.

You could try fabricating a small fuel tank  & line that you hold outside the tractor.  If the tractor runs fine on this, likely above problem.

One other thought.   I've had tractors where the distributor shaft bushings are so worn, the shaft has a lot of sideplay.   This can create lots of problems with the points working correctly, advance, etc causing poor running.   Not worked on a CUB, so may not apply.

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I cant tell you got the engine rpm's up so high that the governor is trying  to pull the rpm's down and surging the motor? 😮 😦🧨

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Thanks for the ideas guys. 

As far as it vapor locking, it doesn't only do it when warm, in the video the tractor had set for about 48 hours and only been run enough to move it from the head to in front of my garage, about 50 feet. My under standing is vapor locking should only happen when the engine is hot, correct?

second the RPMs being set to high I will try running the tractor some at a little below full throttle and see how it runs when I get a chance. My question is what would cause the tractors to be running fine then suddenly running at to high of an RPM.

Brandon

 

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Question;? tractor running fine than suddenly running at to high of and RPM?

Hand control lever to speed control lever on governor, from there the gov. dose all the control, wore gov. will not hold the engine RPMs down, high or low RPMs only, surging, running wild.

I'm right in the middle of doing service and a carb job on my daughters cub. Make sure  fuel flows free to the carb? there is a screen in side the I-H cub carb. it's just inside the inlet fitting, not to many know that, it's top secret, can cause restriction.       photo shows 😎 😲 😁

Stay with us BLee25 and we will clear this up.

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Well IF it's anything like the 6 cubs I have----the load jet plugs up after a little running and you take it out blow thru it good , stick it back in and go til it plugs again. All the filters in the world wont solve the problem either. --- The fine stuff comes from the inside of the carb off of the castings and no way to filter that.  Also no way to actually clean the castings, stuff still comes out and ends up in the jet. --look in the hole in the jet,---a hair can plug it. ---I enlarged mine a bit and that helps to a certain extent. MOST cubs don't get enough gas to run on the stock jet.

Anyway this is what I found on mine!

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Thanks for all your suggestions guys. I have a zenith carb and not an IH. I took the carb all apart and cleaned everything thoroughly. I have only had a chance to run the cub for a few minutes but it was running great. The real test, however, well come the next time I get a chance to mow with it.

 

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Just a final update, after cleaning the carb thoroughly I got a chance yesterday to mow about 3 acres with it and it can great. Hopefully it stays that way.

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Unscrew the cap on the bottom rear of the carb (over the load jet), and drain a little fuel out.  I have one I had to do that on occasion for several months before I got rid of whatever was in the fuel.  I captured it in a cup several times, but no sign of water.  Acted just like yours does.

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