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International Cub quits when choke is turned off.

E

Eldenbrady

New User
Picked up a 71 cub that had something dropped on it so it had been sitting a while (not sure how long). Got everything straightened out and got it started but it surges and stall when I turn the choke off and it has only enough power to move the tractor not to run the mower.

New carb, spark plugs, wires, distributer cap, and coil so it shouldn't be any of those.

I have tried running it for up to half an hour to see if warming it up help but it does no good.

Any ideas would be very helpful.
 
Always trouble shoot then parts never the other way around.
#1 check that you have a good blue/white spark at the center wire of the distributor cp and at each of the plug wires that will jump a 1/4 inch gap or more.
#2 pull the carb drain plug and make sure you have a good steady flow of gas that will fill a pint jar in less then 3 minutes and yes catch the gas to check for dirt and water etc.
#3 check the air cleaner and make sure it is good and clean
 
There was a bunch of trouble shooting that showed I had trouble with the old parts.

Checked the gas multiple time, nice steady flow and clean. Does the same thing with air cleaner disconnected from the carb so I know the air cleaner isn't what is causing it (the air cleaner was one of the things that got bent so I tried without it because I am not positive it is working like it should) Just checked spark jump and it is well over a quarter inch at all connections at the distributor.


 

Try putting the old parts back on! haha.

You probably have a problem with the timing or maybe with the governor since it runs and you've checked the fuel flow. Are you absolutely sure you got the firing order right? It's printed on the tractor. Also, have you checked the compression? Since you have good spark, good fuel flow and assuming carb is good as you say, then probably one of the ones above. Check the compression, and/or pull the valve cover off and make sure the valves are moving.
 
If the intake manifold was disturbed or cracked, the fuel air mixture will be lean. A careful visual check, with a bright LED light source, is a start. Next is an
external fuel in the form of propane, applied around the intake manifold. Use a propane torch with the nozzle removed so only propane comes out, (outside in the yard).
Run it so it is beginning to faulter, then apply the propane. If it picks up speed, you found the issue. Jim
 
A new carb can still get a piece of trash in the jets. Pull the bowl off and clean things up with spray. an old tank is going to have issues. There is a csreen filter
at the carb fitting that is often overlooked. Jim
 

Just get a compression tester (or borrow from parts store) and read the instructions. Most people say take the plugs out of the other cylinders and open the throttle. I think you have to crank for five or so compression strokes to get the right reading. It's pretty easy. Write the readings down and post 'em here and folks will tell you if they look okay.
 
(quoted from post at 18:34:23 07/26/19)
60 on first crank on all cylinders by crank five they are all between 70-75.
Click to expand...

Those readings are in the low range for the bigger tractors. I'm not sure about cub. Someone else will weigh in. Also there should only be a few psi difference between cylinders. Was the engine warm when you did the test?

See what the others say and if the consensus is that these readings are low enough to cause the problem you described above (too low power to run mower) then you might want to re-test the compression with warm engine and add a small amount of oil to each cylinder. If compression improves after adding oil this would indicate your rings are worn and need replacing.

Does the cub smoke and use oil?
 
Imo, use of choke won't compensate for low compression.

I believe there's still something wrong in the carb. I think you will need to do a more thorough cleaning.

I would pull it and soak it in the "half filled gallon paint can" of carb cleaner that an auto parts store will typically have, soak it overnight.

Then make sure you poke thru every passage with something like a wire from a wire tag/paper tag with attaching wire. Could also use a fine strand of copper wire. There are two basic circuits - idle jet and main jet, make sure you follow these thru. Its also a great idea to blow thru everything with compressed air at the very end.

Any tractor that's been sitting awhile has suspect fuel, ideally you would have drained anything that was left at the start but suspect its past that point.
 
The gas tank was dry when I got it, I have since cleaned the tank out and put in fresh gas again so I know gas isn't the problem.

Those compression number were cold with the rest of the spark plugs still in and using a jump pack (cause I drained the battery) and from what I have read both of those things can lower the numbers.
 

It does not smoke, it does have a bit of blowby out the oil dipstick tube but not enough to explain how low the power is.
 
(quoted from post at 09:55:27 07/14/19) Picked up a 71 cub that had something dropped on it so it had been sitting a while (not sure how long). Got everything straightened out and got it started but it surges and stall when I turn the choke off and it has only enough power to move the tractor not to run the mower.

New carb, spark plugs, wires, distributer cap, and coil so it shouldn't be any of those.

I have tried running it for up to half an hour to see if warming it up help but it does no good.

Any ideas would be very helpful.
Click to expand...

My Cub did the same thing. (71 154). I pulled the carb at least 10 times, convinced that this was the problem. It wasn t. I replaced all the usual parts, just like you did, with no results. Finally, I filed the points and set the gap (.013 if I remember correctly). Runs like a champ now.
 
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