Farmall Cub

I bought a 1952 Cub last fall. Used it lightly a couple times and it ran fine. One day it started blowing black liquid out the exhaust, which I thought was oil. I deducted it had a broken oil ring and stopped using it. Recently I decided to take off the head and oil pan and check it out. No broken ring was found. It was standard bore with only about .002" cylinder wear. Rings had an end gap of .045" and the valves felt a little loose in the guides so I replaced the rings (now .020" end gap), valves and guides. It now has 90 lbs compression on each cylinder. I also put a kit in the carb. I put it back together and cranked it up and you guessed it...it is still blowing out black liquid.

I have checked the pipe from the breather to the crankcase and it is clear. I did not replace plugs but they are all firing. I am at a loss as to what to check next. ANY suggestions would be appreciated.

Could it be condensation? I see a lot of cars and trucks that leak water from the exhaust, i know that is condensation. Maybe your tractor has black soot in the pipe that turns the water black. I would taste it to make sure it is not antifreeze and i would let it roll.

Mine gets that also. I don't use it as much and long as I should. It clears up when I do run it for a spell. I'm sure it's condensation. Grump

If it is just shortly after start up, it is probably moisture that has condensed form the hot exhaust coming up through the cool stack and carrying carbon with it. A common problem with vertical exhaust tractors.

i have the same problem on my H, have been told it is just condensation combining with soot, it usually clears up after a bit, i thought it was oil to at first

Thanks Guys,
I ran it up and down some hills and it runs clean when pulling and smokes as it is backing off. Still spitting out black liquid until it warms up. I will just run it some. Maybe the smoke is because the new rings are not seated yet.

Thanks again,

my 530 case does that too, it gets on my face then my wife laughs at me when i come in . i have wondered what it is too.

Yea, I found my problem!! The cub was used at a seasonal recreation facility that my son owns (Colorado Pumpkin Patch) and he uses a lot of young people to help. He had five gallons of diesel fuel for another tractor he had rented and apparently it got put in the cub. I finally figured this out after I spent over $300 on buying rings and a complete valve kit and many hours labor thinking it was a broke ring. I had just about given up hope when I thought of this and ask my son where the 5 gallons of diesel fuel was and he didn't know. I drained it all out and put in a gallon of fresh gasoline and it fired right up and ran clean.

One positive is I now have a rebuilt engine. A fresh rattle can paint job, a new seat cover and we are back in business.

Thanks Guys for all the suggestions. I was just sure it was more than condensation as it started very poorly and the smoke was not stopping.

Sure looks nice for a rattle can job!

Who would have thought that a Cub can run on diesel

Kinda explains the black smoke huh

Nice looking Cub, real nice job for a rattle can

Been a while since I was on this forum but I thought I would post a fairly recent picture of the cub and just one of the ways it is being used (my grandson is driving it for a little leisure at a Colorado Farm Camp that my son's family sponsors.)
Still running good.