H running issues

jaypowers · Oct 9, 2018

Looking for opinions. I have a new to me '41 John Deere H, hand start. Starts fairly easy and idles well. When I get above 2/3s throttle it starts cutting out and sounds like it is missing bad. I may see a puff of black smoke every now and then. It doesn't matter if I am in gear or neutral. It will smooth out and run really well when there is a load on, say going up a big hill in 2nd or 3rd then start to sputter once you get back on level ground.

First thing I tried was new Autolite 3116 plugs. I noticed the old plugs were black which makes me thing it's a carburetor issue. I also cleaned and checked the point gap. I had several friends say that it sounds more like an ignition problem and I should try a condenser first. It has a Wico C magneto. I just replaced the condenser tonight and it made no difference at all. Does this sound like a carb or ignition problem?

What gets me is how smooth it runs up a hill wide open. Any ideas are welcomed and appreciated.

thethresherman · Oct 9, 2018

Sounds like your idle jet setting is too rich. When they are too rich they start fairly well, you won't need to choke it. They will idle fair but carbon up the plugs real fast. When you are running fast and not pulling a load, the carb runs off the idle jet. When you start up a hill and the governor opens up the carb runs more from the load jet. Warm up your engine, then run at fast idle, close load jet gently and count turns. Engine should still run. Now adjust idle jet for smooth running. Once set, open one to two more clicks. Now open load jet back up. Idle tractor down then open throttle quickly, should accelerate without hesitation. My idle jet is about 3/4 turn open on non-ethanol regular gas.

amtrac · Oct 9, 2018

Sounds like you are running too rich. Black smoke is a telltale of that. The engine smooths out under a load because the governor opens up the throttle, effectively giving it more air and leaning out the mix going to the cylinders. Or a timing problem, but I doubt that. It would run badly even under a load. Adjust carburetor and check for clogged air cleaner. Just my humble opinion. See what other H owners have to say, there's a lot of knowledge here.

RandyB(MI) · Oct 9, 2018

If it runs better under load, it is NOT ignition issue. The more load , the more a weak ignition will show up. When it's sitting still at 2/3 throttle, and sputtering etc, add a little choke and see if it smoothes out. I'll bet it will. that says it's lean on the idle circuit. That means either too little fuel or too much leaking air/vacuum . The "too little fuel" can be plugged idle passages in carb or idle needle adjustment needs opened up 1/2 turn. If you open it up and doesn't change then it's not adjustment issue. Air leaks can be sloppy throttle shaft/bushing , worn out throttle blade and bushings not pushed into bore enough. Can also be cracked manifold and/or leaking gaskets. (spray WD 40 around these places to sense leak, engine will smooth out) Set load needle at 1 turn out and idle at 1 1/2 turns out to begin. Carb probably needs re-built. Send me an e-mail if you need that done. My e-mail is open.

jaypowers · Oct 10, 2018

Thanks Everyone. I have not messed with the carb too much yet. I will start there and let you know how it goes.

jaypowers · Oct 10, 2018

I checked my two needles tonight. The idle was out about 1 turn. The load needle was 4 1/2 turns out! I closed it and opened it 1 1/2 out. It ran so much better! It still want wants to cut out some in 3rd gear with wide open throttle. I don't notice it as much in 2nd for some reason. It's not near as bad as it was though. I saw no black smoke tonight.

It also wants to cut out when there is a load on it, like going up a big hill. I tried opening the load needle up to 2 turns out but didn't seem to change it much. I wanted to keep adjusting but it was almost dark out. What should I try next?

Thanks for all the help so far!

amtrac · Oct 12, 2018

Well, you have a 71 year old carburetor. If it is all original, chances are some things in there are worn out. You can adjust all you want, but won't fix the problem. If you have the know how and tools, get a rebuild kit and install it. There are passages inside that need to be cleaned out with a drill bit of the PROPER size. Check GM magazine ads, there are several carb shop advertizers that specialize in tractor carb rebuilding and they most all do a fantastic job. Gotta spend the bucks, but if you have carb problems, more than likely they will fix you up and the machine will run fine.

jaypowers · Oct 12, 2018

Yes, you're correct amtrac, I realize its age. I will probably get the carb professionally rebuilt this winter but I am unwilling to part with it while the weather is decent enough to do something with it.

I asked again since it was way out of adjustment. I wasn't sure if of any tips to tweak it further. The tips I got were fantastic and I appreciate the help.

H running issues

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