John Deere M runs bad

therocker307

New User
Hey everyone I own an old m, and it has a problem. I have gone through the carb several times, put a kit in it, cleaned it, new points, distributer cap, plug wires, plugs, and tested compression in each cylinder. The bugger runs horrible at idle and with no load, needs almost full choke to run, but as soon as you wind her up or start pulling on something,it runs flawless. Ive tried adjusting the carb, and that makes no difference. Any suggestions to try?
 
Sounds like the carb is at fault if you have to run full choke.
Next time you clean it make sure all passages are cleaned out.
A good indication the carb isn't good, is if when you adjust and git no response.
 
I forgot to mention that yo might have a leak in the intake manifold and its causing the tractor to run lean due to inhaling too much air at the wrong place.
 
I am also going to ask what type of plug wires and did you replace the coil? You want good solid core plug wires. If you bought them at Napa, Auto Zone, etc. they are likely not solid core. I got a good set from Agri-Supply last year. I got a flame thrower coil from right here on YT last year and that helped too.

I do agree with Harvey it sounds more like a carb problem to me but last winter I fought my MT for weeks trying to get it to run right. I ended up going through the entire ignition system first based on advice on here. You want to rule out one system before you start messing with another. You have half rebuilt the ignition system at this point, why not finish it up with a new coil, try hotter spark plugs, and make sure to change the button on the side of the distributor as well. Make sure you have solid core plug wires and see what you get. I even replaced my ignition switch when I rebuilt mine.
 
Sure sounds like you missed a hole when cleaning the idle circuit in the carb.

You didn't mention timing. It should be checked every time points are changed. At full speed SPARK should be centered in the timing window. At low idle TC/DC should be close in the window if the dist advance is working properly.
 
Thanks everyone for the recommendations. I have changed the coil, and i will clean the carb again. We have also played with the timing, and it is set good. Come to think of it, it was the 40 that we checked the compression on. This M has a 1/2 way stripped spark plug hole. That may be the problem. I am not going back to the farm until the 28 of this month, so ill try some more things and i have some stuff to fix the plug hole.
 
Using a timing light and getting things set like M-Man said really made my MT run like a top. It starts very easy now. I bought a cheapo old school craftsman timing light on ebay for $15.
 

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