help for John Deere B alfuel

Butch GA.

Member
Have a 1951 John Deere "B" all fuel had carb rebuilt had dist rebuilt. all new wires new plugs.engine will not run smooth it still continues to lope.has black smoke out the exhaust and will not run past idle speed. any help would be GREATLY welcomed.also had govenor reset along with timeing
 
Did the person who rebuilt your carburetor know about the passages in the carburetor, that need to be cleaned out with the correct size drill bits, including the "secret" idle passage?
 
With the bowl off, I believe there is a small brass plug, on the stem, that you remove, (may require some heat), to get at the hole that should be open to the passage that the idle screw is in. When it is open, you should see daylight in the idle passage, with the idle screw removed.
 
Don't rule out the distributor! Does it have a good hot spark? Sounds to me like it doesn't. Check the spark to make sure. If it isnt good and blue, you might need to check point gap and clean or replace plugs. Plug wires in good shape? Is distributor timed correctly? If none of this helps you might replace the condenser and try again. Also, is the carb set right? Start with idle needle 1.5 turns out and the power jet 1 turn out. After you checked all that report back before diving into the carb. All the symptoms you reported lead me to think weak spark, either from faulty components or being out of time. Remember, 90% of carb problems are in the distributor!
Hope this helps. Report back when you can.

Mac
 
I am tending to agree with Mac on this one. Plugged carbs hardly ever overfuel an engine. A little test tho....open idle needle 1 1/2 turns and then once running , shut that load needle all the way and then slowly edge throttle lever open to wide open , which is "fast idle" and should not need any load fuel to do anyway. It is either getting too much fuel from float being stuck and/or a vent passage being plugged OR it is just not burning the fuel it is getting because of ignition problem. You might crack loose the mounting bolts at front and rear and rock it to break seal a little and then turn on fuel at sediment bowl and see if it runs fuel out either end. If it does, it probably isn't ignition problem. If it runs out front only, it's a plugged vent passage.
 
Randy, a similar thing happened to me on my '50 B. I thought it was the carb, but turned out that my points weren't gapped properly, the old condenser had finally quit on me, and the plugs were shot. So, after putting in new (properly gapped) plugs, replacing the condenser, and resetting the points, I had it running like new. I would caution the OP to make double sure the point gap is set to .020 for the Delco distributor rather than the .015 for the Wico mag. Also that the plugs are gapped to .030 and are of good quality, ie AC87 or Autolite 3116. And yes, I know that he said the distributor had been "rebuilt", but what constitutes rebuilt? My money is still on weak spark unless the needle is sticking open causing it to over fuel. But what the heck do I know?

Mac
 
Mac we replaced the points and condenser it has new plugs and wires (copper) centers. It helped a lot. it will Idle now and take fuel to full throttle. How ever at idle speed, engine still has a lope to it. not smooth.
 
Does choking it help or hurt? Do you have to choke it to start it? I know with my B, when you first start it in the morning (especially if it's real cold) will take full choke to start, then have to be left with about 1/4 choke until it warms up or it will lope at idle. When starting hot, there is no lope. Go to full throttle, no lope there either. You might enrich your idle a tad, but I wouldn't go too much until you get her good and hot. Take the old gal out and work the living snot out of her for about 2 or 3 hours, and tweak the carb as you do so. You will notice that the power jet might need some adjustment under load. Best to start lean and go up. Then come back and see if she still lopes at idle. Do you have an operators manual? Only reason I ask is I have a spare if you'd like one. It's for the earlier styled B but the info is mostly the same as the later manual. Only thing different is some of the controls, etc. that were different later on.

Anyhow, hope this helps. And a big THANK YOU for reporting back with your findings! So many here ask questions but we never find out what/if our suggestions work!

Mac
 
Mac
It takes very little choke to start. she starts very easy. sometimes if you leave a little choke on the lope will stop. runs good at high rpm and runs real good under load. I guess the old girl just wants to be cantankerous. again thanks for the feed back. there are some great knowledgeable people on this site and that's the reason I come here for help. thanks
 
Ok...now with a little more info you've gave us...you have either plugged idle fuel passages and / or sloppy throttle shaft / bushings / worn throttle plate. If giving choke smooths it out...it is running lean and WILL lope. Easy test to tell if it needs rebuilt...correctly. Open both needles two turns...start tractor and open it up to 3/4 to full throttle...now close load needle all way..if it stops...it needs rebuilt. simple as that. let us know results.
 
Butch, those carbs can be hard to get set sometimes. But when you finally get there, it's all worth it. I'll defer to Randy, he knows WAY more about 2-cylinder carbs than I ever will. But sounds like you've got most of your problems sorted and Randy has a good idea of what is causing your lope. Glad I could be of some little help.

Mac
 
Randy thank you for all that Information. I will try that, however it could be a few days before I can get Back to work on the tractor.
 
If your throttle plate is worn, it will suck extra air into the engine along with extra fuel which speeds up the engine past idle speed and if conditions are right, the governor will try to slow it down then causing it to lope. The top of the plate should be smooth and round. If it has a narrow high spot like a stem on it, then that is a sign that it has worn into the bushing and should be replaced. Spend $20 on Robert's carb video and it will be the cheapest education you will ever get plus you will learn a lot more about your tractor.
 
Randy we replaced the condenser reset points and some final adjustments to the carb. another new set of plugs. lopes a little when cold but runs pretty good when she gets up to run temperature. again I say thank you to all who responded.
 

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