JD MT Running Rough

[Bobl1958]

Neighbor has a MT John Deere that was his Dads. His Dad passed away and the tractor sat for 10 years in a shed.
Neighbor moved back to the farm and is wanting to play with it. He has had the carb rebuilt by a mechanic, but I don't know how well it was done. I assume he did a good job.
The neighbor also installed new points, condensor, cap, rotor, and also coil with a new battery.

The problem is when you start the tractor it runs like a champ for about 15 minutes, then kind of bogs a little here and there, and may run good for 5 minutes or so, then bogs a little, then runs good again, then may start bogging clear down and the gov is trying to give it more gas, but it's not picking up, and may backfire a couple of times, and then seems to pick back up run good for a few more minutes before starting all over.

I have set the carb settings per the book, but have not had the carb apart. Good fuel flow to the carb.

I am leaning towards a bad new condensor, but wondering also if there could be something in the carb not right. Anyone have thoughts? I asked him to get another new set of points and condensor to start, but am open to thoughts.

When the tractor is running good, it runs real good, but as it warms up is when it starts having issues. Thanks a lot - Bob

 

[old]

Could be the condenser since now days it is common to have a new bad one. Also could be a carb problem. Open the drain plug on the bottom of the carb and make sure you have a good steady flow of gas that will fill a pint jar in less then 3 minutes and 2 is even better

 

[sms]

Sounds to me like a fuel problem. Can there be something in the tank plugging fuel when running?

 

[Geo-TH,In]

X2 fuel issue or a choked screen.
Many old tractors have a screen inside the tank going to the sediment bowl,
Another screed inside the sediment bowl.
A screen in the brass elbow going to the carb..

An add-on inline gas filter can vapor lock on some tractors..

Good luck..

 

[Rich'sToys]

A bad coil can run fine when cold, but then start acting up when it gets warm.
Also, as mentioned, a piece of crud in the gas tank can get sucked down over the opening and restrict fuel flow. Then after the tractor is shut off it floats out of the way. Then the tractor will run good again till the next time it gets sucked down there.

 

[Moonlite37]

Gas cap vented?

 

[Bobl1958]

Further comments...The sediment bowl is clean and the screen in it is clean. I looked in the tank before he ever put fuel in and it was shiney clean.

Took the gasline off at the carb and filled half of a quart coffee can in seconds.

 

[old]

Taking it off at the carb doesn't do any good it needs to get into the carb as in pull the drain plug as siad and make sure the flow if a pint in under 3 minutes.

 

[Steve@Advance]

Revisit the ignition system first, check the distributor for side play in the shaft. If there is any looseness the points will not stay set and do strange things.

Do try the old condenser, look everything over closely for bad connections, shorted wiring, etc.

Feel the coil after it acts up. A proper coil will be about the same temperature as the surrounding components. If it's hot to the touch, it's failing or the wrong coil.

Finally, have a clean glass ready, remove the carb drain plug, catch the flow in the glass. It should start with a full flow, slow some as the bowl empties, but continue to flow a steady stream, not slow to a drip or stop. There should be a screen in the elbow going into the carb, it may be clogged. Look at what is caught, be sure it is clean and water free. Also try loosening the gas cap, the vent may be clogged.

Have you checked the air cleaner? It may be clogged with mud dobbers or bird/rat nests.

One other possibility, sticking valves. Though unusual, they can intermittently stick but usually they have to be worked loose if stuck open. Might take a look, they may be rusted and dry.

 

[donjr]

I had an MT many yeas ago that went into the shop for a final drive shaft. Mechanic dropped the fuel cap behind a bench, and replaced it with a cap they had for a 40. The tractor started starving for fuel. The fuel cap for an MT was vented, where the 40 had a vented tank. Make sure your cap has a hole in it........